Nonlinear Susceptibility in the Spin Glass

The nonlinear susceptibility χ2 in the Ising spin glass near the transition temperature is obtained and compared with those of the Mattis model, pure ferromagnet and pure antifer-romagnet by the Bethe approximation. In the spin glass model, χ2 diverges to negative infinity in both sides of the spin glass transition temperature. Such feature seems to characterize the spin glass transition from other kinds of transitions. We discuss the dependence of χ2 on the dimensionality and frustration in random systems, and compare it with experimental results of random magnets (Ti1−xVx)2O3 and Pt0.98Mn0.02.