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Local magnetic susceptibility of the positive muon in graphite and the quasi 1D spin ½ chain CPC

University of British Columbia

The local electronic structure of the positive muon has been investigated in semimetallic graphite using muon spin rotation/relaxation. Both the muon Knight shift and the spin relaxation rate in highly oriented pyrolytic graphite are anomalously large compared to those in simple metals and both have an unusual temperature dependence. These results indicate that a local moment forms around the muon due to the low carrier density. In contrast, measurements on metallic LiC6 reveal a smaller muon Knight shift which is opposite in sign (negative) and almost temperature independent. We suggest this is due to core polarization of a Mu-Li+ complex. The local magnetic susceptibility around a muon in the quasi one dimensional spin 1/2 antiferromagnetic chain compound CPC has also been investigated. We compare the local spin susceptibility as measured by the muon spin precession frequency with the bulk magnetic susceptibility measured in a SQUID magnetometer. There is a dramatic difference between the local and bulk magnetic response which is in accordance with a recent theory by Eggert and Affleck. This novel behavior can be attributed to a gapless spectrum of magnetic excitations which characterizes spin 1/2 chain compounds and may be considered the magnetic equivalent of the Kondo effect in metals.

Thesis/Dissertation

application/pdf

2009-11-27

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http://hdl.handle.net/2429/15911

Physics

University of British Columbia

UBCV

DSpace