Field dependence of zero-field-cooled magnetization of La 1− xSr xCoO 3 ( x=0.05–0.5)

Abstract

Zero-field-cooled magnetizations with field up to 5000 Oe and temperature up to 250 K were measured for La 1− x Sr x CoO 3 compounds with Sr concentrations of x=0.05, 0.15, 0.2, 0.3, 0.4 and 0.5. It is shown that all M ZFC curves exhibit a maximum at a temperature T a (< T c), which scales well with the power law T a/ T c∝1−( C AT/ T c) H n . The variation of parameter n with the concentration x shows very clearly the existence of two regions bording at a value x c of around 0.18. For the low-Sr region the parameter n does not depend on x and its values are similar to those suggested by the Almaida–Thouless model for canonical spin glass ( n= 2 3 ), whereas in the high x-region n increases monotonically from 0.23 to 0.58, correspondingly, for x varying from 0.2 to 0.5.