Semiconductor spin glasses Cu2Ge13Cr2S4 and Cu0 5In0 5Cr2Se4статья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The compounds Cu2/3Ge1/3Cr2S4 and Cu0.5In0.5Cr2Se4 have been shown to posses magnetic properties characteristic for spin glasses (SG). The critical behaviour of these compounds have been studied by means of the nonlinear susceptibility kci(nl)in the region of freezing temperature Tf that is defined as the temperature of maximum on the kci(nl)(T) curve. The critical exponents gamma, delta and beta have been determined. The temperature Tf' of the maximum on the curves for the dependences of the initial susceptibility on T measured in an ac magnetic field has been found to depend on the frequency of measurements, according to the Vogel-Fulcyer law, the constant T0 being equal to Tf. In these semiconductor compounds the giant negative isotropic magnetoresistance (delta ro)/ro has been observed , that reaches 80% at H = 30bkOe. A maximum in Tf has been observed on the dependence (delta ro)/ro, which is similar to that (delta ro)/ro in the region of magnetic ordering temperature in magnetic semicomductors.