INFLUENCE OF Fe DISTRIBUTION IN THE FECR LAYER ON THE MAGNETIC BEHAVIOR OF THE Fe/Cr/FeCr/Cr/Fe CURIE SWITCH

Abstract

Spintronics is one of the most promising fields of modern electronics. It originated with the discovery of the giant magnetoresistance (GMR) effect and has played a vital role in the development of information recording, storage, and playback systems. Over time, it has become evident that the potential of spintronics is significant: spintronic devices can offer substantial advantages in speed, energy efficiency, and miniaturization compared to their semiconductor counterparts. Many spintronic devices are based on magnetic multilayer structures consisting of magnetic and non-magnetic (a few nanometers thick) metallic layers. The magnetic layers in such structures are coupled by indirect exchange interaction, mediated by conduction electrons. The magnitude and sign of this exchange interaction determine whether the magnetic moments of adjacent ferromagnetic layers, separated by a non-magnetic spacer, align parallel or antiparallel to each other. These properties depend on structural parameters, most notably the thickness of the non-magnetic spacer. The primary challenge is that the spacer thickness is fixed during the fabrication process and cannot be altered during operation. One solution to this problem is the use of Curie switches, which exhibit temperature-dependent exchange interaction due to a diluted magnetic layer embedded within the non-magnetic spacer. Fe(2)/Cr(0.4)/FeCr(0.8)/Cr(0.4)/ Fe(2) structures are well-studied; they have demonstrated a reversal of the exchange coupling sign upon heating, resulting in a change in magnetoresistance. This can be achieved through external heating or even via Joule heating. This work investigates the influence of the morphology of the diluted Fe₁₇.₅Cr₈₂.₅ spacer on its magnetic properties. It is shown that spacer clustering leads to an increased ferromagnetic contribution, the appearance of a small hysteresis loop, and remanent magnetization, which gradually decreases with increasing temperature and causes a shift in the phase transition temperature of the entire Cr/FeCr/Cr spacer. As the temperature increases further, the clusters transition into a superparamagnetic state. It can be concluded that cluster inhomogeneities affect the interlayer exchange interaction: at low temperatures, by inducing direct ferromagnetic interaction through ferromagnetic clusters; at higher temperatures, through their contribution to indirect exchange due to the clusters’ transition to the superparamagnetic state, as well as by shifting the paramagnetic transition point of the entire Cr/FeCr/Cr spacer.