Determination of the FePt thin films magnetic structure by Polarized Neutron Reflectometry

DAFNE GOIJMAN; JAVIER E. GÓMEZ; MARIANO PAULIN; EMILIO DE BIASI; F. OTT; ALEXEI VOROBIEV; A. BUTERA; JULIÁN MILANO

Bariloche

Workshop; International workshop on Spintronics 2022; 2022

Centro Atómico Bariloche

Spintronics is an emerging technology for the next generation of nanoelectronic devices. It looks forward to developing faster and more efficient devices than so far. In particular, ferromagnetic thin films have attracted considerable attention as potential candidates for their application as non-volatile magnetic random access memories, logic devices, and magnetic recording. Some of them present an out-of-plane magnetic anisotropy component mainly determined by magnetocrystalline, magnetoelastic, or interfacial contributions and, they show a magnetic domain structure that forms a striped pattern.In this work, we have studied FePt thin films with different thicknesses by Polarized Neutron Reflectometry (PNR) in order to determine the magnetic depth profile. Experiments were performed in PRISM at The Laboratoire Léon Brillouin (LLB - Saclay) and in SuperADAM at The Institut Laue-Langevin (ILL - Grenoble) in France. To probe magnetic domain structures, the PNR experiments were done at room temperature, and different magnetic fields were applied to obtain several magnetization states (Right figure). The results show that the striped magnetic structure depends on the applied field. Close to remanence, the magnetization component along the applied field presents lower values at the center of the sample with respect to the film edges. For increasing field, the magnetization difference between the center and border regions becomes smaller; and, when the saturated state is attained, the magnetization component is the same along the film growth direction. Simultaneously, we have performed micromagnetic simulations for the same magnetic states that have been experimental probed (Left figure). We have found that the magnetic depth profile observed agrees with that expected for a striped domain structure.Figure 1: Left figure: Magnetic depth profile determined by PNR (black line) and micromagnetic simulations (red line) for FePt film of 60 nm thickness. Right figure: M vs. H loop. The circles indicate the sample magnetic state for each PNR measurement.