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The structure and magnetic properties of some ternary alloys containing manganese and boron Swanson, Max Lynn 1954

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THE STRUCTURE AND MAGNETIC PROPERTIES OF SOME TERNARY ALLOYS CONTAINING MANGANESE AND BORON by MAX LYNN SWANSON  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF'SCIENCE  in the Department of METALLURGY  We accept this thesis as conforming to the standard required from candidates for the degree of MASTER OF SCIENCE.  Members of the Department of Metallurgy.  THE UNIVERSITY OF BRITISH COLUMBIA October, 1954.  ABSTRACT  Binary alloys of manganese and boron and ternary a l l o y s of manganese and boron with aluminum, zinc, t i n and indium were prepared.  Their structures were determined from x-ray powder  photographs, and t h e i r ferromagnetic properties were measured with a Sucksmith r i n f balance, using a powerful electromagnet.  The  orthorhombic phase MnB had a ferromagnetic Bohr magneton number of 1.73 per molecule and a Curie point of 309°C.  Most of the ternary  alloys were s l i g h t l y ferromagnetic, but no strongly ferromagnetic single phase regions were found.  Paramagnetic measurements on Heusler alloys showed that they followed the Curie-Weiss law f o r the. r e s t r i c t e d range of temperature i n which measurements could be made.  ACKNOWLEDGMENTS  The author i s grateful for assistance rendered by members of the staff of the Metallurgy department, especially his research director, Dr. H. Myers, and Mr. R. Butters. The work was done with the help of funds provided by the Defense Research Board under Research Grant 281.  TABLE OF CONTENTS Page I.  INTRODUCTION  II.  MAGNETIC MEASUREMENTS  t  Theory ..  1  5  Apparatus. ,  •>•  5  III.  X-RAY MEASUREMENTS  9  IV.  SUMMARY OF WORK DONE  10  V.  PREPARATION OF ALLOYS  11  VI.  RESULTS 1. Manganese-Boron alloys 2.  Manganese-Aluminum-Boron  13 alloys  3. Manganese-Zinc-Boron alloys 4.  . . . . . . . . . .  21  . . . . . . . . . . . .  23  Manganese-Tin and Manganese-Tin-Boron alloys . . . .  27  5. Manganese-Indium and Manganese-Indium-Boron alloys .  30  VII.  PARAMAGNETIC ^ASUREMEKTS ON.HEUSLER. ALLOYS  VIII.  DISCUSSION  IX.  BIBLIOGRAPHY  OF RESULTS  AND  CONCLUSIONS  31  38 41  ILLUSTRATIONS  Page 1.  The ferromagnetic r i n g balance  2.  Pole pieces producing a uniform f i e l d gradient  3.  Ferromagnetic Curie point determination f o r MnB  4.  Magnetic moment per unit mass divided by saturation moment, CT/tf  . . . . . . . . . . . .  7 7 17  against absolute temperature divided by ferromagnetic  0  Curie point, T/Op 5.  18  The determination of the saturation moment at absolute zero of MnB« «  0  « e « s o o e o o o o o o e e  9  0  *  0  0  0  0  •  •  •  •  •  6.  The paramagnetism of MnB  7.  Manganese-aluminum-boron ternary diagram showing phases at room temperature,  8.  o o o . . . . . . . . .  20  «  o  .  .  .  .  .  .  22  .  Manganese-zinc-boron ternary diagram showing phases at room temperature  9.  . o o o .  19  •  . . . . . . . . . . . . . . . . . .  . . . . . . . .  25  Manganese-tin-boron ternary diagram showing phases at room temperature  29  10.  The paramagnetism of Cu MnIn  11.  The paramagnetism of Cu MnAl  35  12.  The paramagnetism of CuaMnAl  36  13.  The paramagnetism of Cu MnSn  37  2  2  2  •  34  THE STRUCTURE AND MAGNETIC PROPERTIES OF SOME TERNARY ALLOYS CONTAINING MANGANESE AND BORON  I.  INTRODUCTION  It was assumed by Langevin that a paramagnetic substance consisted of non-interacting atoms or molecules, each having a permanent magnetic moment.  I f i n a magnetic f i e l d these moments are d i s t r i b u t e d  s t a t i s t i c a l l y , the magnetic s u s c e p t i b i l i t y of the substance i s s  X  (D  = T  where C i s the Curie constant of the substance, and T i s the absolute temperature.  i s defined as the magnetic moment per unit mass, C  ,  divided by the applied f i e l d , H. Weiss modified the Langevin theory by considering that 1 interactions between atoms  produced an i n t e r n a l f i e l d which was pro-  p o r t i o n a l to the magnetisation or magnetic moment.per unit volume, I . This f i e l d , NI, i s added t o the external f i e l d to give the e f f e c t i v e field: H  e  -  H + NI  N i s the Weiss inter-molecular f i e l d constant.  The Curie-Weiss law  r e s u l t s from s u b s t i t u t i n g t h i s e f f e c t i v e f i e l d f o r the applied f i e l d :'. i n equation ( l ) :  2  6 i s the paramagnetic C u r i e p o i n t .  F o r a gram m o l e c u l a r w e i g h t o f  substance,  o • N/> cr ? ,  N^C  Ql  3 RM  M  M  where y » i s t h e d e n s i t y ,  i s the gram m o l e c u l a r s a t u r a t i o n  moment, R i s t h e gas c o n s t a n t  and M i s t h e m o l e c u l a r w e i g h t .  I f N 'and t h u s because,  & a r e p o s i t i v e , t h e substance i s  as can be shown, t h e r e may e x i s t below T = 0  magnetisation i n the substance.  zero.  e q u a t i o n (2) i s t r u e , and t h e s u b s t a n c e i s  i n different  ferromagnetic, spontaneous  T h i s m a g n e t i s a t i o n i n c r e a s e s as T d e c r e a s e s ,  a p p r o a c h i n g a maximum as T approaches  The spontaneous  a  magnetic  F o r T g r e a t e r t h a n 9, paramagnetic.  m a g n e t i s a t i o n o f a body i s d i r e c t e d d i f f e r e n t l y  r e g i o n s , c a l l e d domains.  The r e s u l t a n t  magnetisation i s  because o f t h e random d i s t r i b u t i o n o f t h e magnetic d i r e c t i o n s . relatively small external f i e l d  zero,  Only a  i s r e q u i r e d t o l i n e up t h e d i r e c t i o n s o f  m a g n e t i s a t i o n , and t h u s make t h e body f e r r o m a g n e t i c as a w h o l e .  E x p e r i m e n t a l e v i d e n c e ( e s p e c i a l l y gyromagnetic r a t i o  measure--  ments) i n d i c a t e s t h a t t h e magnetic moment f o r f e r r o m a g n e t i c s u b s t a n c e s i s caused by e l e c t r o n s p i n . magneton,  -  eh ZtfTinc  The moment o f a s p i n n i n g e l e c t r o n i s one Bohr  = 9.27 x 10 ' e r g / g a u s s , Z  where e and m are t h e  and mass o f t h e e l e c t r o n , and h i s P l a n c k ' s c o n s t a n t .  A pair of electron  s p i n s can be d i r e c t e d o n l y p a r a l l e l o r a n t i p a r a l l e l .  If interactions  a n e x c e s s o f s p i n moments t o p o i n t i n one d i r e c t i o n ,  spontaneous  magnetisation  charge  cause  exists.  The c o l l e c t i v e e l e c t r o n t h e o r y p r e s e n t s a model o f the m e t a l l i c s t a t e w h i c h i s more r e a l i s t i c t h a n t h a t o f W e i s s ,  Outer e l e c t r o n s o f  atoms are t h o u g h t o f as s h a r e d c o l l e c t i v e l y t h r o u g h t h e s u b s t a n c e .  Although  3.  this model leads to satisfactory results for simple substances, such as nickel and its alloys with copper, the quantum mechanical problems involved in the study of more complex substances are too d i f f i c u l t to be solved. Atomic interactions are mainly due to the outer electron shells.  Heisenberg postulated that the exchange interaction energy  between the same shells (i.e.? 3d shells of transition metals) of adjacent atoms could be positive, i n which case the electrons line up with parallel spins, producing ferromagnetism.  This postulate has had  as yet no quantitative theoretical verification.  Zener^, on the contrary,  postulated that the exchange energy between adjacent atociic 3d shells of transition metals was always negative, and that ferromagnetism was caused by coupling between 3d and As shell electrons of the same atom. The results of this assumption are not i n good agreement with observed properties. Using Heisenberg*s postulate, Slater^ and Bethe have assumed the following variation of the exchange energy, J, with the ratio of the internuclear distance, D, to the 3d shell diameter, d. —-ryCo  O  It i s seen from this curve that the exchange energy i s positive and large enough to cause ferromagnetism for values of D/d slightly greater than 1.55 (e.g.* Fe, Co and Ni).  Thus paramagnetic  manganese, with a r a t i o only s l i g h t l y less than 1.55, could become ferromagnetic i f i t s internuclear distance were increased so that D/d became greater than 1.55o  This increase occurs f o r ferromagnetic  manganese alloys and compounds: Alloy: D/d  :  Cu MnIn  Cu MnAl  2.98  2.84  2  2  Cu MnSn 2  2.97  Previous work i n the U n i v e r s i t y of B r i t i s h Columbia Metallurgy department has shown that an ordered face-centered cubic ferromagnetic phase occurs i n the ternary alloys of manganese and carbon with a metal (X) having high valency and a positive size factor with respect to manganese.  Aluminum, zinc, t i n and indium were used success-  f u l l y i n t h i s capacity.  The optimum composition f o r t h i s phase i s MnaXCj  carbon occupies the body centered p o s i t i o n .  This work suggests that s i m i l a r a l l o y s with the carbon replaced by boron or nitrogen may e x i s t .  In the work to be described,  boron alloys with s i m i l a r structures and magnetic properties t o those containing carbon were sought.  L i t t l e i s known about binary boron  a l l o y s and none about the ternary a l l o y s considered.  5. II.  MAGNETIC MEASUREMENTS  Theory.  Magnetic measurements of the saturation magnetic moment per unit mass, CT , and the s u s c e p t i b i l i t y ,  , were required.  The  p r i n c i p l e f o r the determination of these quantities i s the measurement of the force exerted on a specimen of mass m when placed i n an inhomogeneous magnetic f i e l d .  This force i s :  F = CTm  a_H  =Xm  H  d-x The method used was having unknown CT and jC  based on a comparison of the specimen  with a standard substance.  If H ^ H  i s kept  constant while the force i s being measured f o r the specimen and t h e standard, CT and .X H3 H  , since  9-X  can be determined without knowing the value of  • X;  m^  — F  Apparatus;  2  (a)  -*» "2 The Magnet:  The magnetic f i e l d was produced by an electromagnet of the Weiss type, b u i l t by R. Shier and G. Kidson^ while i n t h i s department. A maximum f i e l d of 21,500 gauss could be a t t a i n e d . To produce a constant v e r t i c a l f i e l d gradient, the pole pieces were shaped as shown i n f i g u r e 2.  "  :  (b)  The Ferromagnetic  Balance:  The force exerted on a ferromagnetic specimen placed i n t h e region of constant f i e l d gradient was measured using a Sucksmith  ring  6. balance (Figure 1 ) . The d e f l e c t i o n of a l i g h t beam r e f l e c t e d from mirrors suitably attached to the beryllium copper r i n g was proportional to the force d i s t o r t i n g the r i n g .  A molybdenum rod was used to connect  the r i n g t o a platinum i r i d i u m c o l l a r , into which a c y l i n d r i c a l platinum i r i d i u m specimen box could be placed.  A very convenient  specimen size of only t h i r t y milligrams was normally needed.  Pure i r o n  was used as a standard.  (c)  The Paramagnetic Apparatus;  The paramagnetic apparatus d i f f e r e d from the ferromagnetic apparatus only i n the following p a r t i c u l a r s ! (i) (ii) (iii)  the balance was s i m i l a r but more s e n s i t i v e , the molybdenum rod was replaced by a s i l i c a tube, the specimen was e i t h e r machined into a r i n g shape o r carried i n a carbon capsule.  I t was attached by means  of a wire clamp placed i n a groove at the bottom of the s i l i c a tube (see sketch), v  ;! „  s i l i c a tube specimen clamp thermocouple  A specimen s i z e of only 100 mg. was adequate. specimen c a r r i e r d e f l e c t i o n s .  Allowance was made f o r  Nickel was used f o r c a l i b r a t i o n .  Some sizes f o r the r i n g balance are: Ring diameter » 6 cm. Ferromagnetic r i n g : 3 mm. by o,3 mm. thick; s p i r a l springs: 0.3 mm. t h i c k . Paramagnetic r i n g : 3 mm. by o . l mm. thick; s p i r a l springs: 0 l mm. t h i c k . o  -Q  Balance Mirrors  Microscope  Beryllium Copper Ring  O i l Damping  ••*  n=H^[]--C3^  Molybdenum rod  - F l a t S p i r a l Springs  Specimen Box Figure 1:  The., ferromagnetic r i n g balance  _ uniform f i e l d _ gradient  Figure 2s  Pole pieces producing a uniform field  gradient.  8. (d)  High and Low Temperature Apparatus:  For low temperature magnetic measurements the specimen was suspended just above l i q u i d oxygen i n a Dewar f l a s k .  A copper-constantan  thermocouple i n conjunction with a potentiometer, a standard c e l l and a galvanometer was used t o measure the temperature. High temperature measurements were made i n a s p e c i a l l y constructed water cooled furnace. A platinum-platinum rhodium thermos couple was used. The r i n g balances and high and low temperature apparatus were b u i l t by H. Myers and R. Butters of t h i s  department.  9.  III.  X-RAY MEASUREMENTS  A P h i l i p ' s x-ray machine and Straumanis type powder cameras were used t o take photographs of samples of a l l the a l l o y s .  The  r e s u l t i n g Debye-Scherrer powder patterns were measured. Film shrinkage effects were eliminated by r e f e r r i n g a l l distances t o that distance known to correspond t o a Bragg angle of 9 0 ° . 2 The films were indexed by using the r a t i o s of the s i n 9 values o f the l i n e s ; the equation f o r sin^O sir^O  =  7?  where 9 i s the Bragg angle, ^  i n the cubic system i s :  ( 2 + 2 + ]2) h  k  i s the wave length of the x - r a d i a t i o n ,  a i s the parameter of the unit c e l l , and h, k , 1 are the indices of the r e f l e c t i n g plane.  Parameters were calculated from the same equation,  and plotted against the T a y l o r - S i n c l a i r function to eliminate the e r r o r caused by absorption of x-rays by the specimen.  IV.  SUMMARY OF WORK DONE.  The following a l l o y systems were investigated:  1.  Mn - B  2. Mn - A l - B 3. Mn - Zn - B 4. Mn - Sn - B 5. Mn - In - B Other binary a l l o y s were made t o a i d i n i d e n t i f i c a t i o n of phases.  Magnetic measurements were made on ferromagnetic a l l o y s ,  MnB i n p a r t i c u l a r . Paramagnetic measurements were also made f o r some Heusler alloys.  u  V.  PREPARATION OF ALLOYS  Two methods of preparation were used: (1)  Induction Melting: The a l l o y components were heated i n alumina crucibles under  argon at atmospheric pressure by induced eddy currents. c h i l l cast i n t o a brass mould i f possible.  The melts were  The r e s u l t i n g ingots were  homogenized i n evacuated s i l i c a tubes or under an argon atmosphere. Samples were mounted i n l u c i t e and examined microscopically. (2)  Sintering: Because of the d i f f i c u l t y i n melting by induction alloys,  containing zinc or a large proportion of boron, they were prepared by s i n t e r i n g intimately ground mixtures of t h e i r components. The mixtures were heated i n evacuated s i l i c a tubes containing very l i t t l e free volume.  1  The following a l l o y s were sintered:  Sinter Components  Alloy  Temperature (°C)  Time (hr.)  •  MnB  Mn;B  MnAl B  950  - 1050  72  MnAlgjB  900  MnAl ;MnjB  900  MnjZnjB  900  72  MnSnB  MnSn;B  600  75  MnlnB  MnlnjB  1000  48  2  Mn Al3Bn 6  A l l Mn-Zn-B  ;  2  72 ,  72  "  12  The materials used i n the preparation of the a l l o y s were: Manganese:  99.9% purity, donated by the Electromanganese Corporation of America.  Aluminum : 99.99$ purity, donated by the Aluminum Company of Canada. Zinc  : dust; 93$ purity (major impurity being oxygen)  Tin  :  99.99% purity  Indium  :  99.99% purity, donated by the Consolidated Mining and Smelting Company of Canada.  Copper  :  100.0$ purity  Boron  :  'pure amorphous' and 99.2$ purity.  13.VI. RESULTS  1. Manganese-Boron Alloys; Previous Work; Heusler  6  (1904), Jassoneix (1906) and Wedekind (1907) 7  f i r s t investigated manganese-boron alloys.  8  They reported that only  MnB was ferromagnetic. H. Forestier and M. Graff (1936) found the Curie point of MnB to be about 300°C. R. Hocart and M. F a l l o t  1 0  (1936) evaluated the  moment of the manganese atom i n MnB at 9.65 (* 5%) Weiss magnetons; they discovered the structure to be orthorhombic with eight MnB per unit c e l l and with parameters a = 2 95> b = 11.5, c = 4.10A. 0  R. K i e s s l i n g MnB  11  (1950) found four manganese-boron phases:  : orthorhombic: a = 5.560, b «= 2.977, c = 4.145A with 4 MnB per c e l l .  Mn B4. 3  : orthorhombic: a = 3.032, b = 12.86, c « 2.960A with 2 Mn B4 per c e l l . 3  Mn B 2  : tetragonal: a = 5.148, c = 4.208A with 4 Mn B 2  per c e l l . to^l*  :  orthorhombic: a = 14.53, b = 7.29, c w 4.21A with 8 Mn^B per c e l l .  Only MnB was ferromagnetic.  14.  Results:  The r e s u l t s are tabulated: Heat Treatment  Alloy  Phases at Room Temperature  Ferromagnetism strong  c h i l l cast; homogenized sintered  MnB; Mn B MnB  homogenized 50 h r s . at 1000°C.  MnB; Mn B  <T =100  Mn gB4.  homogenized 50 hrs. at 1000°C.  Mn B; MnB  oj , = 50  Mn B  homogenized 50 h r s . at 1000°C.  Mn B; Mn^B;-©* - Mn  Mn B  c h i l l cast homogenized 50 hrs.at 1000°C  Mn B; <<- Mn Mn B; Mru,.B; << - Mn  homogenized '50 hrs.at 1000°C.  Mn^B; e< - Mn  MnB  Mn «B 5  5  4 6  2  2  3  2  o  2  2  2  2  2  (f =147} 0 = 309° C 0  F  0  None . None None None  The phases MnB, Mn B and M n ^ had the same structures and 2  parameters as those found by K i e s s l i n g . The ^ - manganese phase seemed to be almost as stable as the Mn B and Mn^jB phases, since i t occurred i n the 2  a l l o y s Mn B, Mn B and Mn^B even a f t e r homogenization. .It i s possible that 2  3  impurities i n the boron s t a b i l i z e d the  «i - Mn phase.  The sintered a l l o y MnB was single phase, but the induction melted MnB, which was only s l i g h t l y o f f composition, had a l i t t l e Mn B 2  phase present.  Thus the range of composition f o r the single phase, MnB,  i s narrow. Magnetic Properties: The magnetic properties o f the MnB phase were investigated f o r two d i f f e r e n t specimens: (l) mass, &  For the f i r s t specimen, the magnetic moment per unit  , was 136 ergs per gram per oersted at 20°C.(measured using a  f i e l d of 16,000 gauss).  I f CT i s plotted against absolute temperature  15.  squared, T  , at low temperatures, a straight l i n e r e s u l t s , which  when extrapolated to absolute zero gives the saturation moment, 0'o . Such a l i n e was plotted f o r the MnB specimen, using temperatures down to 140°Kj the r e s u l t i n g value of &o was 1 4 7 . The ferromagnetic Bohr magneton number f o r a molecule of a substance having gram molecular weight M i s P  B  " 6 5 . 7 5 x 147 = 1.73/t 5585  Pg  = M 0t> .  For the  MnB,  5585 B  per MnB molecule,  or per manganese atom.  For purposes of comparison, t h i s i s almost i d e n t i c a l with the value f o r pure cobalt: Pg  = 1.72 .  The ferromagnetic Curie point, 9 p , of MnB was determined byplotting  CT against T (Figure 3 ) . %  This plot produces a s t r a i g h t l i n e  near the Curie point, which was found to be 3G9°C. Also,  °/ (f f  0  was plotted against T/9p (Figure 4 ) .  As t h i s  curve i s generally structure s e n s i t i v e , the plot f o r MnB d i f f e r e d from that f o r n i c k e l . (2)  For the second specimen the r e s u l t s were:  cr =  132  cr = 143 (Figure 5)j P 0  9  F  B  = 1.68  = 304°C.  This specimen probably had a small amount of a second phase present.  Paramagnetic measurements were made on t h i s MnB The paramagnetism followed the Curie-Weiss law (Figure 6):  specimen.  16  The values calculated f o r the constants were s C = 1,48 x 10" gram and the paramagnetic  Curie point, 9 = 305°C,  This value agrees  w e l l with the ferromagnetic Curie point of 304°C, . The  paramagnetic  Bohr magneton number, Pg  = 2,828 VCM  P  The r a t i o between t h i s value and the f e r r o -  B  = 2,79 per molecule.  magnetic Bohr magneton number, 1.68,  per molecule.  per  For KnB,  i s of the usual order of magnitude.  17.  -  - 7000  120 -  - 6000  140  1 1  •v  ^  I  V  100  - 5000 m  \  \  v \  1 1  ^\ v h  80 - •  \  4000  \ \ \  \ l \\  60  -  40  -  •  o  - 3000  2000 \  V 20  p 0 : <? against T • : C against T  - 1000  z  •  150  200  250  0 300  T(°C.)  Figure 3: Ferromagnetic Curie point determination f o r MnB ( f i r s t specimen): Magnetic jnoment per unit mass, CT. and moment squared, CT, against temperature, T.  18.  1.00  0.80  0.60  0.40  0.20 O •  0.20  MnB Nickel  0.6a,  0.40  1.00  0.80  T/e,  Figure 4:  Magnetic moment per unit mass divided by , saturation moment , cf/tT  0  , against  temperature divided by ferromagnetic Curie point, T/Op,.  absolute  130  U  0  1  15,000  1  30,000  J  45,000  L  60,000  1  75,000  TVK.)  Figure 5: The determination of the saturation moment at absolute zero of MnB (second specimen): Magnetic moment per unit mass,0", against 2  absolute temperature squared, T •  20.  4.0  •  I  I  450  550  Temp, decreasing  T(°C.)  ±J  I  _ J 650  Figure 6 : The paramagnetism of MnB  750  850  (second specimen):  The inverse of s u s c e p t i b i l i t y , 1/x  (X i s measured i n  ergs; per gram per oersted), against temperature, T.  21.  2.  Mangane s e-Aluminum-Boron.- Alloys  Previous Works  No previous work has been done on Mn-Al-B a l l o y s . The 12  phase diagram of the Mn-Al system  i s w e l l known.  Results; A l l a l l o y s were homogenized f o r 50 h r s . at 800 t o 1000"C. The main phases occurring were^-manganese, MnB, Mn B, and the body2  centered cubic  3" phase of the manganese-aluminum  system (Figure 7 ) .  The Mn B phase had s l i g h t l y larger parameters than i t had i n the binary 2  alloys.  The r e s u l t s were as follows; The a l l o y MnAl was made i n order t o obtain the Heat Treatment  Alloy  3  as-cast homogenized  Mn Al B 3  6  slight  -Mn; cubic  2?  Mn^.sAl^.5B  Fe rromagnet ism  Phases at Room Temperature /3  Mh Al B 6  phase.  2  cr= 15.7;© = 310°C F  MnB  slight hone  Mn Al B  y ;MnB  Mri Al B  r ;MnB  medium  MnB  3  2  2  2  C = 43.9;6^ = 310°C  Mn^lB  /3 -Mn; Mn B  slight medium none  Mn AlB  /3 -Mn; Mn B  none  MhAl B 2  as-cast homogenized or sintered  2  2  3  Mn . AlB 2  Mn AlB 2  Mn  as-cast homogenized  5  1>5  -  AlB  MnAlB MneAlaBii  MnB;/? -Mn / ?-Mn;MnB;MnB T ,MnB ?  5 , MnB  as-cast homogenized sintered  MnB  medium  <r =  27.0  cr= 56.9;6 - 310°C F  ^=67.3' cr  = 6 6 . 0 ;j  none  r = 22.9; ^=71.2  22. Mn  80  kMn*B Mn B 3  Mn  /  30  70  •  Mn B 2  /3 -Mn + M n B  B  2  /3-Mn  •  •  60  /  ,40  \  /tf-Mn+_MnaB + MnB  o  50 S'  0 40  MnAl  + MnB  O  I  a  •  30  o 20  A. 80  70  60  40  50  30  Al  F i g u r e 7s  Manganese-Aluminum-Boron T e r n a r y Diagram Showing Phases a t Room Temperature  • O  denotes non-ferromagnetic a l l o y denotes ferromagnetic a l l o y  20  10  23.  Where no heat t r e a t m e n t i s g i v e n i n t h e T a b l e , t h e a l l o y s had t h e same s t r u c t u r e s before and a f t e r h o m o g e n i z a t i o n , and t h e magnetic measurements a p p l y t o t h e homogenized a l l o y s . I t i s seen t h a t the a l l o y s M n A l B , M n A l B , M n . s A l B and 3  6  2  2  MnAlB are t h e o n l y ones h a v i n g u n s t a b l e phases i n t h e a s - c a s t The i m p o r t a n t u n s t a b l e  state.  phase i s MnB, w h i c h forms r e a d i l y i n a l l o y s  w i t h h i g h boron and low manganese  content.  The f e r r o m a g n e t i s m o f the M n - A l - B a l l o y s p r e p a r e d was l a r g e l y due t o t h e MnB p h a s e . 3. Manganese-Zinc-Boron-Alloys. P r e v i o u s Work;  No p r e v i o u s work has been done on Mn-Zn-B a l l o y s .  F o r t h e Mn-Zn s y s t e m , t h e phase d i a g r a m from z e r o t o weight percent  z i n c was s t u d i e d by E . P o t t e r and R . H u b e r ^ (1949).  Room t e m p e r a t u r e phases were is  face-centered  fifty  ot - Mn; /3 - Mn, and  «< - Z n .  c u b i c w i t h f o u r atoms per u n i t c e l l .  by d e c o m p o s i t i o n o f  £  <* - Zn  I t i s formed  (which i s c l o s e packed h e x a g o n a l w i t h two  atoms per u n i t c e l l ) o n l y a f t e r v e r y s l o w c o o l i n g t o room t e m p e r a t u r e . The phase d i a g r a m from f i f t y t o one hundred w e i g h t z i n c was s t u d i e d by S c h r a m m ^ (1940).  percent  24.  Results; The a l l o y s were s l i g h t l y f e r r o m a g n e t i c f o r a l a r g e range o f composition. The a l l o y s and t h e i r p r o p e r t i e s a r e l i s t e d ( F i g u r e  Alloy  Phases at Room Temperature  Brittleness  8):  Ferromagnetism 'medium '  Mni]_Zn B  2  50% ot - Mnj 45% 8  malleable  Mn Zn B  2  60% « f - Mnj 30%. 9  malleable  slight  Mn ZnB  75% /3 - Mnj 25% Mn*B  brittle  none  Mn ZnB  75% Mri^B  Mn ZnB  50% ^ - Mn; 50% M n ^  Mn^ZnB  50% oi - Mn; 25% Mn^B; 25%, I  MnZnB  50% K  7  d  1 0  6  3  2  slightly  brittle  brittle  slight • very  brittle  slight  medium  brittle  C = 56, C = 6 4 ; 0  60% Z n ; 30% SL  malleable  remanent none  75% Mn B  brittle  medium  MnQZnB^o  80% <p  brittle  Mn Zn B  70% <j> ; 30% SX.  Mn ZnB 0 5  Mn]_oZn B 3  8  2  7  4  brittle  !  1 0  (f = 104; remanent strong;remanent  O n l y the f i r s t two l i s t e d a l l o y s r e q u i r e d a n n e a l i n g  after  f i l i n g t o produce good x - r a y p h o t o g r a p h s . Phases o c c u r r i n g were: (1) /3 - Mn and Mn^B: These phases are w e l l known. (2) B o d y - c e n t e r e d to  t< _ Mn, and had parameters a  f o r Mn ZnB, 2  o(. - Mn types  cubic Q  T h i s phase was s i m i l a r  = 8,888 A f o r Mn„ Zn7B and a 2  I t was s l i g h t l y t e t r a g o n a l f o r t h e M h Z n B 8  1 0  2  Q  alloy.  (3) 6 , a c u b i c s t r u c t u r e , p r o b a b l y o r d e r e d f a c e - c e n t e r e d Its  parameter was 3.918A f o r Mni]Zn7B . 2  ®  w  a  s  = 9.169A*  cubic:  probably ferromagnetic only  25.  •*  Figure 8:  Zn  Manganese-zinc-boron ternary diagram showing phases at room temperature.  • O  denotes non-ferromagnetia-alloy denotes ferromagnetic a l l o y  26.  i n the ordered state, since most of the ferromagnetism of Mn^Zn7B  2  was l o s t by f i l i n g , (4)  The pure zinc phase l i s t e d f o r the a l l o y Mn  0>5  ZnB:  This i s possibly not pure zinc, but a phase with the same structure and parameters, (Such phases occurred f o r the Mn-Sn-B and Mn-In-B systems). (5)  -ft- , a non-magnetic phase of unknown structure  occurring i n the' a l l o y s Mn (6) The  0  The 0  t;ZnB and MngZnaB^Q  0  Q  and \\  phases, which were strongly ferromagnetic:  phase was almost as magnetic as MnB.  MngZnB^o & an  I t occurred i n the a l l o y s  MngZn B , which were prepared t o demonstrate that zinc 2  /0  would not replace manganese t o any appreciable extent i n MnB, phase was present i n the a l l o y s Mn  n  had complidated structures.  ZnB and MnZnB,  Both  The J\  (j> and h  27.  4.  Manganese-Tin and Kanganese-Tin-Boron A l l o y s .  Previous Works Potter  1 5  and N i a l  The manganese-tin system has been investigated by  (1931), G u i l l a u d 1 8  (1943), Nowotny and S c h u b e r t  1 6  17  (1943)  (1947). Potter found f o r a l l o y s annealed at 450 to 500°Cs Mnj^Sn was' weakly ferromagnetic with Op = 150°C. Mn Sn was strongly ferromagnetic with 9p = 0°C. 2  MnSn  was not ferromagnetic.  Nowotny and Schubert reported the following structures: MnnSn  ; cph. with 2a = 5.65, c = 4-506A, - = 1.595  3  s a = 4.392 - 4.370, c = 5.457 - 5.475A,  Mn Sn 2  c = 1.242 - 1.250j c r y s t a l i o g r a p h i c a l l y l i k e the a • f i l l e d up» NiAs type. MnSn  s tetragonal with a = 6.647, c <= 5.434A, - = 0.817. a  2  N i a l found the same phases with almost the same parameters except that Mn]jSn had a = 5.66A 3  Results:  A. The following Mn-Sn alloys were melted: Alloy  Phases at Room Temperature  Ferromagnetism  MnSn  75% MnSn ; 25% Mn Sn  medium at low temp..  Mn Sn  90% Mn Sn  medium at low temp.  Mn^Sn  90$ Mn  medium at low temp.  2  2  2  2  1:L  Sn3  The phases MnSn , Mn Sn and Mn„ S n had the same parameters as 2  found by N i a l .  2  3  28  B,  Mn-Sn-B a l l o y s prepared were (Figure 9)s  Mn-^SnB  80%/Q  Mn SnB  Ferromagnetism  Brittleness  Phases at Room Temp,  Alloy  brittle  none  75% M n ^ n a  brittle  medium at low temp.  Mn SnB  75% Mn Sn  brittle  medium at low temp.  MnSnB  80% 0 ; 2 0 % MnSn  Mn^SnsBa  80% Mn Sn  Mn^Sn B5  Mn^rilZt?  6  3  - Mn  2  2  3  0".= 33.8; remanent  malleable  2  brittle  medium at low temp.  50% Mn Bj 3 0 % Mn Sn (possibly unstable)  brittle  medium at low temp.  70% Sn; 2 0 % MnSn  malleable  s l i g h t at low temp.  2  2  2  2  o  The /3 - Mn phase of Mn-j^SnB  n  a  d  parameter, a  Q  = 6.488AV  The 9 phase was body-centered tetragonal with the same parameters as pure tins a = 5.831, c = 3.181A. This phase was the only ferromagnetic phase found, other than the binary Mn - Sn phases.  I t was strongly remanent.  29.  Figure 9s ,Manganese-tin-boron t e r n a r y diagram showing phases a t room t e m p e r a t u r e .  • O  denotes n o n - f e r r o m a g n e t i c a l l o y denotes f e r r o m a g n e t i c a l l o y  30.  5.  Manganese-Indium and Manganese-Indium-Boron Alloys.  Previous Works the  Z w i c k e r ^ (1951) found room temperature phases f o r  Mn-In system to be o< - Mn, Mn In and indium; 3  3  20  V 0  Mn In had a  - brass structure.  Shirokoff's  results agreed with these,  except that the a l l o y Mn^In had a magnetic phases were found.  - Mn structure.  No f e r r o -  Goeddel and Y o s t ^ l (1951), however,  reported ferromagnetism from 3 t o 55 weight percent manganese. Results;  A.  Mn-In a l l o y s prepared were:  Alloy  Phases at Room Temp.  Mn In  /3  Mn In  y  9  3  The  Ferromagnetism  very b r i t t l e  none  brittle  none  very malleable  none  - Mn  iT i  Mnln  Brittleness  In  Y phase was that previously reported.  These r e s u l t s agree  with those of Shirokoff. B,. Mn-In-B a l l o y s prepared were; Alloy  Phases at Room Temp.  Mn InB  50% y ; 40% Mn B  brittle  none  Mn InB  60% Mn B; 30% In  malleable  none  MnlnB  90% 9  malleable  medium  6  3  /3 magnetic  2  2  Brittleness  Ferromagnetism  - Mn could be retained i n MtiglnB by quenching.  The f e r r o -  9 . phase had the same structure and almost the same parameters  as indium, which i s face-centered tetragonal with a = 4.594A  and  c - 4.951A. This phase corresponds to the 9 phase of the Mn-Sn-B system.  31.  VII.  Procedure?  PARAMAGNETIC MEASUREMENTS ON HEUSLER ALLOYS.  S i n g l e phase H e u s l e r a l l o y s were p r e p a r e d by i n d u c t i o n  m e l t i n g and were homogenized.  Powders were a n n e a l e d and r a p i d l y  quenched t o r e t a i n the o r d e r e d s i n g l e Results;  phase.  The f o l l o w i n g a l l o y s were p r e p a r e d :  Alloy  Annealing Temp, ( C)  Parameter (A)  8  Cu MnIn  530  6.2084  Cu MnAl  800  5.9502  Cu  850  5.9167  Cu MnSn  680  6.1654  Cu-^MngSna  640  2  2  „ Mn ^Al 2.97 0,982 2  Paramagnetic measurements were made on the f i r s t four l i s t e d a l l o y s while they were cooling from temperatures points.  The inverse of the s u s c e p t i b i l i t y ,  near t h e i r melting w  a  s  plotted against  temperature, T, giving the following r e s u l t s :  1.  The curve (Figure 10) f o r Cu MnIn was s l i g h t l y convex 2  toward the temperature phases.  This behaviour i s common f o r ferromagnetic  The Curie-Weiss law was used f o r a straight l i n e drawn through  the high temperature 0  axis.  = 328°C.  points to calculates C - 1.41 x 10  (The ferromagnetic Curie point i s 233°C).  Bohr magneton number was calculated to be. 5.78/Cg  The paramagnetic  per molecule.  value compares favourably with the ferromagnetic value, per manganese atom.  per gram and  p  B  This  = 4j4/tg  32.  2. were s i m i l a r .  The curves (Figures 11 and 12) f o r Cu MnAl and Cu MnAl 2  Both had straight l i n e sections f o r a range of 200°C  above the Curie point, and thus obeyed the Curie-Weiss range.  3  law f o r t h i s  The calculated constants were? Cu MnAl i 2  C = 4.96 x 10" 3 per gram; 0 = 283°C.  —  Cu MnAl s 3  C • 4.85 x 10~3 per gram; 0 - 175°C.  The ferromagnetic Curie point, 0 , of Cu KnAl i s 330°C. p  As 0 i s  2  p  generally almost the same as the paramagnetic Curie point, 6, these two values c o n f l i c t .  However, when Cu MnAl was cooled r a p i d l y , the 2  curve was depressed toward the temperature axis, and 0 was raised to 350°C (+ 10°), which i s about the expected value.  The difference  between the two curves f o r Cu MnAl was probably caused by a loss of 2  order i n the more slowly cooled a l l o y .  No such difference occurred  f o r Cu MnAl. 3  3.  The curve (Figure 13) f o r Cu MnSn was a straight l i n e 2  from 400 to 600°C.  The constants weres  C = 3.92 x 10~  3  per gram.  Q - 219°C. The discrepancy between t h i s value of 0 and 340°C f o r 0  p  i s possibly  caused by a loss of order i n Cu MnSn while cooling. 2  At 390°C (* 5°) the d i r e c t i o n of the curve changed sharply, with } C decreasing, i n d i c a t i n g a rapid transformation t o a non-ferromagnetic phase.  The X-ray photograph v e r i f i e d t h i s conclusion.  This  result  illustrates the use of magnetic measurements for phai  boundary determinations„  34.  300  328  e=I  400  500  600  T  F i g u r e 10s The paramagnetism o f C u M n I n : 2  The i n v e r s e o f s u s c e p t i b i l i t y , 1/jC  ( X i s measured i n  ergs per gram per o e r s t e d ) , a g a i n s t t e m p e r a t u r e , T ( ° C , ) ,  35.  T(°C.) Figure l i s The paramagnetism of Cu MnAl; 2  The inverse of s u s c e p t i b i l i t y , 1/x  ( X i s measured  i n ergs per gram per oersted), against temperature, T.  36.  Figure 12: The paramagnetism of Cu MnAl: 3  The inverse of s u s c e p t i b i l i t y , 1,6c ( X i s measured i n ergs per gram per oersted), against temperature, T.  37.  Figure 13s The paramagnetism of Cu MhSn; 2  The inverse of s u s c e p t i b i l i t y , 1/JC  l s  measured i n  ergs per gram per oersted), against temperature, T.  38. VIII.  1,  DISCUSSION OF RESULTS AND CONCLUSIONS  The s a t u r a t i o n magnetic moment a t a b s o l u t e z e r o  temperature  f o r t h e p u r e r specimen o f MnB used was 147 ergs per gram per T h i s r e s u l t may be as much as two p e r c e n t  oersted.  l o w , because o f the  p o s s i b i l i t y o f a s m a l l amount o f a second phase b e i n g p r e s e n t . f e r r o m a g n e t i c Bohr magneton number was 1.73 jM ( a l m o s t t h e same as the v a l u e f o r c o b a l t ) .  B  The  p e r MnB m o l e c u l e  T h i s v a l u e i s the same  as t h a t c a l c u l a t e d f o r manganese when i t forms d s j r o c t a h e d r a l bonds. A l t h o u g h o c t a h e d r a l bonds are not formed i n MnB ( w h i c h has t h e orthorhombic s t r u c t u r e  same  as F e B ) , each manganese atom i s s u r r o u n d e d by  f o u r atoms a t 2.67A and two a t 2 . 7 0 A .  Thus s i m i l a r b o n d i n g p r o b a b l y  occurs. The f e r r o m a g n e t i c C u r i e p o i n t o f MnB was 309°G,-' as compared w i t h 1120°C f o r f a c e - c e n t e r e d  c u b i c c o b a l t . The paramagnetism o f MnB  f o l l o w e d the C u r i e - W e i s s law c l o s e l y ; was t h e same as t h e f e r r o m a g n e t i c  2.  t h e paramagnetic C u r i e p o i n t  one.  The t e r n a r y a l l o y s i n v e s t i g a t e d c o n t a i n e d s e v e r a l f e r r o -  magnetic t e r n a r y p h a s e s . (1)  Some w h i c h m e r i t f u r t h e r  i n v e s t i g a t i o n are:  The 9 phases o c c u r r i n g i n t h e a l l o y s MnSnB and M n l n B . These phases, parameters  b e s i d e s h a v i n g t h e same s t r u c t u r e s  as t i n and i n d i u m , had a l m o s t t h e same l i n e  i n t e n s i t i e s on t h e x - r a y p h o t o g r a p h s .  They were  m a l l e a b l e , but r e t a i n e d t h e i r magnetism a f t e r working.  and  cold  (2)  The cubic 0 phase of the Mn-Zn-B system, occurring f o r alloys with boron content of ten atomic percent.  This  phase was apparently ferromagnetic only i n the ordered state, and became disordered when cold worked. (3)  The phase, of unknown structure, occurring i n the a l l o y Mn6Al B-u. 3  This phase had a lov; Curie point, since the  magnetic moment per unit mass was more than three times greater at absolute zero than at room temperature.  It  was the only Mn-Al-B phase found with a Curie point near room temperature. The f a c t that there were no ferromagnetic phases l i k e the ordered face-centered cubic Mn XC phases (where X i s A l , Zn, Sn or In 3  and carbon i s i n the body-centered position) can be explained i n terms of s i z e - f a c t o r s .  Hagg has found that, i n general, i n t e r s t i t i a l  binary compounds have simple structures only i f the r a t i o of the atomic diameter of the small atom to that of the large atom i s less than Thus i r o n and nitrogen, with a r a t i o of 0.56, structure;  0,59,  sho'uld form a simple  they a c t u a l l y do, since Fe^N has the same structure as the  Mn XC phases, with nitrogen i n the body-centered p o s i t i o n . 3  This structure i s unstable f o r Mn^C,  since the r a t i o f o r  manganese and carbon i s just at the c r i t i c a l value of 0.59.  By r e -  placing some of the manganese atoms with larger atoms, the average diameter of the m e t a l l i c atoms i s increased.  Thus the r a t i o of the  carbon diameter to the metal diameter can be lowered below  0.59,  creating the simple face-centered cubic structure, by the addition of only a small amount of another metal, X.  Because the diameter of boron  40  is greater than that of carbon, the ratio for manganese and boron i s increased to 0.67, and Mn^B forms a complicated structure.  Moreover,  even i f enough larger metal atoms are used to produce the composition, MnaXB, the ratio w i l l s t i l l be greater than 0.59 and the simple facecentered cubic structure w i l l be unstable. The atomic diameters used for this discussion are: Element:  Fe  Mn  In  Sn  Zn  Al  Atomic Diameter:  2.48  2.6  3.24  3.02  2.66  2.86  N  C  1.40  1.54  B 1.74  T h e effect of boron on the alloys investigated might also be explained i n terms of i t s electrochemical properties.  Boron often occurs  in rows or sheets in i t s allo7/s, and thus has a strong tendencjr to bond with i t s e l f .  Therefore, since the i n t e r s t i t i a l atoms i n the Mn XC 3  phases are as far separated from one another as possible, boron would not l i k e l y occupy such positions. 3.  The results of the paramagnetic measurements on the Heusler  alloys were inconclusive, because of the phase transformations and the loss of ordering at elevated temperatures. Most of the uncertainty was probably caused by the ordering effects.  41, BIBLIOGRAPHY  1.  P. Weiss, Jour, Phys, (4), 6, 661.  2.  C. Zener, Phys. Rev. 81, 440,  3.  J . S l a t e r , Phys. Rev. ;$6, 57.  4.  H.P. Myers, Doctor of Philosophy Thesis, University of S h e f f i e l d , (1950).  5.  G. Kidson, Masters Thesis, University of B r i t i s h Columbia, (1953).  6. F . Heusle'r, Z e i t . f . Angew. Chem. 1£> 260. 7. B. Jassoneix, Compt. Rend. 142. 1336. 8.  £. Wedekind, Ber. deut. Chem. Ges. 4JD, 1259.  9.  H. Forestier and M. Graff, Compt. Rend. 203. 1006.  10.  R. Hocart and M. F a l l o t , Compt. Rend. 203. 1062.  11.. R..Kiessling,  Acta Chemica Scandinavia  146.  12.. W. Fink and L. Willey, American Soc. Metals Handbook, H 6 3 (1948), H. P h i l l i p s , J . Inst. Metals 6£, 275. 13... E. Potter and R. Huber, Trans. American Soc. Metals £1, 1001. 14.  J . Schramm, Z. Metallkunde 3_2, 399.  15.  H. Potter, P h i l . Mag. (7), 12, 255.  16.  C. Guillaud, Thesis, Strasbourg, 1 (1943).  17.  H. Nowotny and K. Schubert, Naturwissenschaften }\»  18.  0. N i a l , Svensk Kern. T i d . 5J, 165.  19.  U. Zwicker, Z. Metallkunde j j l , 399.  20.  G. Shirokoff, Masters Thesis, University of B r i t i s h Columbia, (1953).  21.  W. Goeddel and D. Yost, Phys. Rev. 82, 555.  582.  

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