Femtosecond laser machining of high permeability permalloy

Abstract

For the multi-core orthogonal fluxgate magnetic field sensor, in which the sensor sensitivity increases exponentially with the number of cores in the sensing element, a micro/nano multi-core structured high permeability magnetic material, such as permalloy, is expected. A permalloy sheet can be formed into such a multi-core structure material by laser machining if the magnetic properties are not damaged. In this study, the effects of femtosecond laser machining of permalloy on the magnetic properties of the machined permalloy workpiece are investigated. The results show that changes in the coercivity of the machined permalloy workpiece are dependent on the surface morphology modification induced by the femtosecond laser. It appears that there is a laser fluence threshold for the permalloy coercivity to decrease to a minimum (as indicated by the formation of ripples on the machined surface), beyond which the coercivity will increases with the laser fluence at a gradual rate. Copyright © 2012 Inderscience Enterprises Ltd.