Ferromagnetic Alloys: Magnetoresistance, Microstructure, Magnetism, and Beyond (Review)

Abstract

When suitably alloyed, ferromagnetic-nonmagnetic (FM-NM) and ferromagnetic-ferromagnetic (FMFM) alloys display remarkable saturation magnetization and magnetoresistance (MR). They also possess the ability to form well defined, unique micro and nano structures over a wide temperature range, and when prepared under closely controlled condition. This review aims to provide insights on how to synthesize macro and nano structures from the nano particles Co-Ag, Co-Cu, Co-Au, and Fe-Co alloys under controlled condition and explores magnetic and MR characteristics of thus synthesized micro and nano alloy structures - including giant MR, and saturation magnetization. Fabrication of these alloy based micro and nano structures was conducted using pulse-current deposition. Characterization was carried out using vibrating sample magnetometer, X-ray diffractometer (XRD), and rf-SQUID meter. XRD profiles and other characteristics of variously prepared nanostructures are compared in terms of particle size and lattice constant. Results suggest that both the increase in MR and saturation magnetization in FM-FM based alloys strongly depend on particle size and lattice constant in micro and nano structures. This manuscript reviews the presence of a variety of MR effects in nano-structures of FM-NM alloys and it also investigates the relationship between saturation magnetization, alloy composition, and lattice constant, also referred to as crystallographic state of the constituent element, employing phase diagram. Results presented in this review suggest that these nano-structures can potentially be employed to create next generation of bio-magnetic devices for bio-medical and electronic applications due to the ease of fabrication and low cost associated with their preparation as opposed to presently available similar material used for biomedical application.