Low-temperature magnetic properties and the crystallization behavior of FINEMET alloy

Abstract

We have synthesized FINEMET alloy by a melt spinning technique and studied in detail its crystallization behavior and low-temperature magnetic properties. The crystallization behavior is characterized by transmission electron microscopy and Mössbauer spectroscopy. At early stages bcc solid solution precipitates from the amorphous matrix. At later stages, they order to yield DO3 ordered Fe3Si coexisting with a small amount of Fe2B. The analysis of Mössbauer spectra supports this observation. The temperature dependence of the magnetization in the temperature range 10–300 K of the FINEMET alloy in its as-quenched state follows the relation M(T)=M0(T) (1−B T3/2−C T5/2−⋅⋅⋅), which is indicative of the presence of spin wave excitations in the alloy. The value of the C/B ratio and the mean-square value of the range of exchange interaction ⟨r2⟩ are found to be characteristic of the noncrystalline ferromagnets. The small value obtained for the exchange stiffness constant D is an indication of the softening of the exchange interaction.