Multipeak ferromagnetic resonance behaviour tailored by magnetoelastic coupling in FeSiB/CoNi layered microwires

Abstract

The aim of this work is to report on the influence of the presence of a magnetically hard layer with large thickness on the ferromagnetic resonance (FMR) behaviour of soft/hard biphase microwires. Such microwires consist of a FeSiB soft nucleus, an intermediate glass layer and a CoNi hard outer shell, and are prepared by the combined quenching and drawing technique with electrochemical deposition. The unusual FMR response observed for this biphase system is characterized by the presence of a multipeak absorption spectrum that depends on the static field and on the thickness of the hard phase by means of magnetoelastic coupling. For a thick enough CoNi layer, the internal stresses induced in the nucleus during the electroplating process are very strong, giving rise to three electromagnetic absorptions: one at a low frequency related to the CoNi shell and two at higher frequencies corresponding to the FeSiB nucleus which are ascribed to two well-defined magnetization regions with different magnetic anisotropies.