Depth resolved interfacial magnetic spin spiral at (111)-La_0.7Sr_0.3MnO₃/LaFeO₃ epitaxial thin films

To probe the emerging switchable magnetic spin spiral at the antiferromagnetic LaFeO₃ (LFO) layer due to interfacial effect with element specificity in (111)-La_0.7Sr_0.3MnO₃ (LSMO)/LaFeO3 epitaxial thin films we utilise a resonant soft X-ray reflectivity (RSXR) technique providing axial sensitivity. This emerging magnetism and magnetic anisotropy control at the ferromagnet (FM) /antiferromagnet (AFM) interface in perovskite transition metal oxides is interesting for spintronics applications. However, studies of magnetic interactions at heterostructure interfaces are often limited by direct measurements, especially of AF spin structures. Here, we present a novel method of probe the spin structure at the AF layer on oxide heterostructures.

(111) pc-LSMO/LFO fully single crystalline heterostructures were epitaxially grown on (101) DyScO3 substrates by pulsed laser deposition as our model system to probe the spin alignment at the antiferromagnetic LaFeO3 layer. Vibrating sample magnetometer measurements confirmed bulk ferromagnetism. RSXR data was collected at Advanced Light Source beamline 4.0.2 at Lawrence Berkeley Lab using linear polarized X- rays at 600-800 eV, with applied magnetic field parallel to the sample surface within the scattering plane using permanent magnet. Data analysis was carried out with RemagX using the magnetic matrix formalism.

RSXR data were recorded at the Fe L3 edge (708.32 eV) for the bilayer along LSMO easy and hard axis. From fitting the preliminary data on the bilayered samples, the model with a spin spiral reproduced the spin structure of the system with a weakly pronounced cross-over at Qz = 0.125 nm-1. Furthermore, a characteristic top/dip at Qz = 0.18 nm-1 in the asymmetry is reversed for the easy and hard axis, which can only be attained by axial switching indicating a directional transition in spin spirals. This suggests a translation of ferromagnetic momenta from the LSMO layer to LFO due to exchange coupling at the interface, which is controllable by rotating the applied field. We demonstratethat RSXR with linearly polarised light presents a unique means of resolving FM and AFM spins at buried interfaces in multistructures, providing valuable details about the spin texture that are necessary in order to exploit emerging interfacial phenomena towards applications.