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UBC Theses and Dissertations

Optical detection of spin-bath relaxation in Eu2 doped calcium fluoride Clarke, Thomas E.

Abstract

The magneto-optical Faraday effect was used, to observe the spin-bath relaxation in Europium doped CaF₂ crystals at helium temperatures from 1.5 to 4.2° K. Theory shows that the magnitude of the Faraday rotation is proportional to the difference in population of the ground state doublet. The experimental method used in this thesis is the same as that which was successfully used by Glattli and by Griffiths. Pulsed microwave power at X-band frequencies was employed to disturb the equilibrium between the spin system and the bath. The observed relaxation time t was expected to have a T⁻¹ temperature dependence hut because of the orientation of the crystal in our dc magnetic field which resulted in the seven transition lines being close together, cross-relaxation effects produced a temperature dependence of approximately T⁻². It is suggested that exchange coupled pairs of Eu²⁺ and clusters involving Eu³⁺ may account for this temperature dependence rather than there being a phonon bottleneck present. The field dependence of the relaxation time was found not to be directly related to the resonance spectrum, The Eu²⁺ concentration of the crystals used in this thesis was .2%

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