THEORY OF MAGNETIZATION AND EXCHANGE-ENHANCED SUSCEPTIBILITY OF PD-NI ALLOYS

A recently developed new formalism is used to calculate the temperature-dependent, exchange-enhanced Pauli susceptibility, χP(c,T), of paramagnetic and weakly ferromagnetic Pd-Ni alloys. For the first time both the strong nonlinear effects of local chemical environment and of moment formation are included in the calculation of χP(c,T). Also, the effects of quantum and thermal spin fluctuations are included for the first time in alloy calculations away from the dilute limit. This is done through the use of a semiphenomenological theory consistent with scaling laws and with the results of renormalization-group theory for the single-impurity problem. In order to compare theory with experiment, we analyzed the theoretical results for χP(c,T) in exactly the same way as the experimental results. Two different calculational methods were used, one corresponding to an expansion in powers of the Ni concentration and the other involving the exact embedding of 55-site clusters in a self-consistently determined effective medium. Both methods yielded results superior to those of all previous theories and in good agreement with experiment.