Magnetic Properties of CoFeSiB/(Co, CoPtRh) Multilayer Microwires

The magnetic and magnetotransport properties have been investigated in a family of multilayer glass-coated microwires with a soft CoFeSiB nucleus and magnetically harder Co and CoPtRh deposited outer layers. Their magnetic properties are mainly determined by the magnetic interactions between the magnetic phases, i.e., the magnetoelastic coupling generated by the supplementary mechanical stresses induced by the deposited layers and by the magnetostatic interactions between the soft magnetic inner core and the hard magnetic deposited layers. The deposition of 900 nm-thick hard magnetic layers (Co and CoPtRh) on the soft magnetic CoFeSiB glass-coated microwire leads to a biphase magnetic character. Isothermal annealing at 300 °C for 1 h of multilayer microwires determines a slight decrease of the coercive field, an increase in the relative magnetic permeability, and to an increase in the magnetoimpedance response, more significant for the CoFeSiB/Co multilayer microwires. The possibility to design the magnetic and magnetotransport properties through magnetic coupling and annealing makes these materials very competitive as the functional sensing elements.