Magnetization distribution in an amorphous ferromagnet

Abstract

Experimental results of magnetization and M\"ossbauer measurements on an amorphous alloy ${\mathrm{Fe}}_{75}$${\mathrm{P}}_{15}$${\mathrm{C}}_{10}$ are presented to show that there is a sizable fluctuation in exchange interaction in amorphous ferromagnets. Like several other amorphous ferromagnetic alloys, the spontaneous magnetization as a function of the reduced temperature for the amorphous alloy falls characteristically below those of crystalline ferromagnets such as ${\mathrm{Fe}}_{3}$P and Fe. A comparison of the magnetization data with Hadrich's theory for amorphous ferromagnets suggests that in the amorphous alloy the average variation in the exchange constant ($J$) can be as large as $J$ itself. The M\"ossbauer spectrum is analyzed in terms of a distribution of hyperfine fields which suggests a spatial distribution of magnetization that is compatible with the exchange fluctuation as deduced from the temperature dependence of magnetization. The origin of magnetization fluctuation in amorphous alloys is discussed. It is pointed out that a broad distribution of magnetic ordering is consistent with the experimental observation of the coexistence of Kondo-type resistance minimum and ferromagnetism in amorphous alloys.