ANISOTROPY ENERGY OF SPIN-GLASSES AT T LESS-THAN TG STUDIED BY TRANSVERSE SUSCEPTIBILITY

An investigation of the anisotropic properties of CuMn, AgMn, CuMnAu//x, AuFe spin glasses at T less than T//g by performing transverse susceptibility (X PERPEND ) measurements in zero and small ( APP 1STH 1 kG) static field H//o//z is described demonstrating that, in presence of a remanent magnetization sigma initially developed along z, the response of the spin system to a small transverse ( PERPEND z) field involves a collective rotation of the spins which is fully characterized by a macroscopic anisotropy field H//A for small deviations. At a given temperature the anisotropy energy K equals sigma H//A is found independent of sigma . A slight decrease of K with temperature is evidenced in the investigated range T less than equivalent to T//g/3. At T VM LS TH T//g the same value for K is found to explain //X// PERPEND , NMR and ESR (both in presence of remanence and in the zero field cooled state). In cases where can be reversed by the application of a negative field H//0, analysis of X PERPEND data in the states with sigma up and down, in addition to hysteresis cycles studies, suggests that the total anisotropy energy might be the sum of uniaxial and unidirectional contributions. The anisotropy energy per atom is found to scale as the Mn concentration c in CuMn and AgMn and to increase linearly with the Au concentration x in ternary alloys, in qualitative agreement with theoretical predictions.