Site-specific measurement of the giant magnetoresistance (GMR) of individual NiFe/Pt multilayers nanowires

Abstract

As devices shrink, there is a requirement to characterize the magnetic properties of individual inhomogeneous nanosized components. Here the site-specific giant magnetoresistance (GMR) of individual NiFe/Pt multilayer nanowires has been evaluated in the current perpendicular to plane (CPP) geometry using a new in-situ method directly inside a scanning electron microscope (SEM). In this method a controlled magnetic field is produced directly inside the SEM using a custom designed electromagnet. Two nanomanipulators equipped with sharp tips enable the site-specific measurement of the resistance of individual nanowires in the gap between the coils as the field is varied. The CPP-GMR measurement of ~70 nm diameter individual NiFe/Pt multilayer nanowires shows that, at 500 Oe, the nanowires have a magnetoresistance effect of up to 5.8 % dependant on the nanowire layer thicknesses and magnetic field orientation. This in-situ method of GMR measurement enables precise nanocharacterisation of magnetoresistance of nanowires as a function of local nanowire microstructure, geometry, length, and field orientation, whilst concurrently allowing the observation of any changes to the microstructure.