Critical exponents of amorphous Gd/sub 0.70/Pd/sub 0.30/

The magnetization of liquid-quenched amorphous Gd/sub 0.70/Pd/sub 0.30/ was measured between temperatures of 77 and 300 K in fields up to 6 kOe. The ferromagnetic Curie temperature T/sub C/ and the critical exponents β, γ, and delta were found to be 131.77 +- 0.20 K, 0.34 +- 0.02, 1.010 +- 0.003, and 3.95 +- 0.10, respectively. These experimentally determined values of the critical exponents very clearly satisfy the scaling law γ = β(delta-1). Of special interest is the value of unity for γ in the neighborhood of the ferromagnetic Curie temperature, the usual Curie-Weiss plot of inverse susceptibility yielding a paramagnetic Curie temperature of 155.20 +- 0.20 K. EPR measurements made over the temperature range of 135 to 100 K reveal an almost-free Gd3+-ion response broadened and made asymmetric by conduction-electron effects, while at the same time exhibiting no significant directional dependence on the applied field. This result and the lack of hysteresis at 77 K support the idea that liquid-quenched Gd/sub 0.70/Pd/sub 0.30/ becomes an isotropic amorphous ferromagnet at T/sub C/. Finally, examination of sections of a given sample (produced via the hammer-and-anvil technique) reveal that, even at the highest cooling rates (approx.107 K s-1), entirely amorphous material may be produced only toward the sample edges, in agreement with current models of amorphous cooling in liquid-quenched samples