NMR study of the crystallization kinetics in FINEMET-type materials

We have investigated the evolution of the structural and magnetic properties of Fe(Si)-based (FINEMET-type) nanocrystalline alloys using the NMR technique at zero field. NMR is a technique which provides structural information on different local atomic environments, and also allows the evaluation of the local magnetic anisotropy. Melt-spun ribbons of Fe 73.5Cu 1Nb 3Si (22.5− x) B x ( x=4, 6, and 9), which contain both amorphous and crystalline phases were studied as a function of the annealing temperatures ( T A). The 93Nb and 11B resonances were observed, and the magnetic stiffness associated with different local environments of 93Nb nuclei were determined. We observed that the Nb frequencies decrease with increasing T A, which suggests that Nb atoms migrate from either Fe-rich regions to Fe-poorer regions or to the B-richer phases. The local measurement of the anisotropy as a function of T A shows an equivalence to the behavior of the bulk coercivity as a function of T A.