Control of the magnetization in pre-patterned half-metallic La0.7Sr0.3MnO3 nanostructures

Abstract

The evolution of the magnetization configurations in highly spin polarized La0.7Sr0.3MnO3 (LSMO) thin film elements (20–60 nm in thickness) as a function of external magnetic field and temperature is studied by direct magnetic imaging using x-ray magnetic circular dichroism photoemission electron microscopy. The sample structuring is done via a pre-patterning process using a Cr mask layer. The LSMO grows amorphous on the Cr layer for the 20 nm thick film but polycrystalline at larger thicknesses. Temperature dependent studies allow for a direct comparison of the properties of the strained and unstrained LSMO regions on a single sample and show that the polycrystalline areas exhibit a higher TC compared to the epitaxial areas. The single crystalline areas are largely magnetically decoupled from the matrix. The magnetic switching between domain states and domain wall spin structures is determined for LSMO ring elements of varying size and thickness. We find that the magnetic field values required to depin domain walls or to nucleate domains increase with decreasing ring width due to the increasing role of shape anisotropy and edge defects. Both transverse and vortex domain walls are stable spin configurations at room temperature and at zero field. In particular, we demonstrate that the desired domain wall type can be selected by applying an appropriate field sequence.