Critical Properties of a Random-Anisotropy Systema−DyNi: A New Universality Class in Disordered Systems?

The scaling properties of a random-anisotropy system (amorphous DyNi) are given for the first time. The phase transition is shown to be of the spin-glass type, with a divergence of the nonlinear magnetization. However, critical exponents are different from those of canonical Heisenberg spin-glasses (e.g., CuMn or $a-\mathrm{GdAl}$). This result strongly suggests that random-anisotropy systems belong to a different universality class. This allows us to understand the scatter observed in the exponents of different Heisenberg spin-glasses as caused by a hyperscaling crossover near the freezing temperature.