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.

Nanoscale Mapping of the Magnetic Properties of (111)-Oriented La0.67Sr0.33MnO3

“…A variety of techniques have previously been used to image the magnetic domain structure of LSMO films and nanostructures, including Kerr microscopy, magnetic force microscopy, − scanning electron microscopy, and photoemission electron microscopy; − however, these techniques are either limited in terms of spatial resolution, which is typically tens of nanometers or are purely surface sensitive and therefore blind to bulk structures. Conversely, Lorentz transmission electron microscopy (TEM) can image the subsurface magnetic structure of a thin film or nanostructure , in projection or by the use of cross sections.…”

Deterministic domain wall rotation in a strain mediated FeGaB/PMN-PT asymmetrical ring structure for manipulating trapped magnetic nanoparticles in a fluidic environment

“…Such transitions occur because generated stress anisotropy energy modifies the DW magnetization configuration to move it to a more stable state. 19,53 This signifies that O–V DWs are stable than O–T DWs when stress anisotropy is the dominant contributor to the total energy. Because of the simulation limit, the exact voltage where O–T to O–V transition occurs can not be determined.…”

Efficient spin transfer torque in La2/3Sr1/3MnO3 nanostructures

“…11,12 La 2/3 Sr 1/3 MnO 3 (LSMO) is a promising half-metallic material that in recent experiments with geometrically confined structures has shown a low magnetocrystalline anisotropy, allowing one to tailor the spin structure and displace domain walls with low pinning. 13,14 Furthermore, the moderately high Curie temperature (T C %360 K for thin films), 15 which is above room temperature, allows one to study STT even close to the magnetic phase transition where material parameters like the saturation magnetization M S reach effectively zero, adding an additional experimentally tunable parameter. So far, reports on the interaction of spin-polarized charge carriers and magnetization (including STT) in LSMO or related perovskites are indirect 16,17 or at relatively high current densities in point contacts 18 and, given the promising prerequisites, a motivation for studying this material has become clear.…”

“…Assuming a spin polarization P close to 100%, 29 a saturation magnetization of M s ¼ 320 kA/m obtained from SQUID data for an equivalent LSMO thin film 30 and using a domain wall width D of 0.5 lm, which we determined from PEEM measurements for 2 lm wide ring structures, 13,14 we obtain from 26 e ¼ pbP h 2eM s D ;…”