Susceptibility data on an amorphous GdAl spin-glass show an irreversibility onset line t=-A-H2/φ- and a susceptibility crossover line t=+A+H2/φ+ (t is reduced temperature; H is field). The exponents φ are both close to 3, and the amplitudes A differ only by a factor of 2. In contrast to earlier explanations of the irreversibility in terms of a de Almeida-Thouless mean-field instability, here both crossovers are explained in terms of a non-mean-field scaling theory.
Malozemoff, A. P.; Barnes, S. E.; and Barbara, B., "Non-Mean-Field Interpretation of the Irreversibility Line in Spin-Glasses" (1983). Physics Articles and Papers. 53.