Finite-temperature theory of local environment effects in amorphous and liquid magnetic alloys

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Abstract
A finite-temperature theory of magnetism that takes into account the fluctuations of local magnetic moments due to structural disorder is presented on the basis of the functional-integral method and the method of the distribution function. The theory describes qualitatively or semiquantitatively the finite-temperature magnetism of liquid and amorphous metals and alloys as well as the substitutional alloys in a wide range of electron-electron interaction strength from metal to insulator. The results of numerical calculations are presented for amorphous iron. The local environment effects on the density of states, local magnetic moment, susceptibility, and amplitude of local moment are examined. It is found that amorphous iron forms an itinerant-electron spin glass at low temperatures because of the nonlinear magnetic coupling between Fe local moments and the local environment effect on the amplitude of the Fe local moment due to the structural disorder. The calculated spin-glass temperature (100 K) is in good agreement with the value extrapolated from experimental data on Fe-rich amorphous alloys.