Controlling antiferromagnetic domains in patterned La0.7Sr0.3FeO3 thin films

Abstract

Transition metal oxide thin films and heterostructures are promising platforms to achieve full control of the antiferromagnetic (AFM) domain structure in patterned features as needed for AFM spintronic devices. In this work, soft x-ray photoemission electron microscopy was utilized to image AFM domains in micromagnets patterned into La 0.7 Sr 0.3 FeO 3 (LSFO) thin films and La 0.7 Sr 0.3 MnO 3 (LSMO)/LSFO superlattices. A delicate balance exists between magnetocrystalline anisotropy, shape anisotropy, and exchange interactions such that the AFM domain structure can be controlled using parameters such as LSFO and LSMO layer thickness, micromagnet shape, and temperature. In LSFO thin films, shape anisotropy gains importance only in micromagnets where at least one extended edge is aligned parallel to an AFM easy axis. In contrast, in the limit of ultrathin LSFO layers in the LSMO/LSFO superlattice, shape anisotropy effects dominate such the AFM spin axes at micromagnet edges can be aligned along any in-plane crystallographic direction.

Uniaxial Néel vector control in perovskite oxide thin films by anisotropic strain engineering

“…Hence, the data indicate either a sample with domains larger than the field of view (20 × 20 μm 2 ) or a thin film with macroscopic uniaxial magnetic anisotropy. Literature values for AF domain sizes are typically submicron to a few microns of scale, as reported for LFO [35,37,39], LSFO [58,68], NiO [69,70], CuMnAs [16], and Mn 2 Au [17], substantially smaller than the field of view in this paper. Hence, consistent with a crystallographic monodomain state from RSM, the XMLD-XPEEM data point toward macroscopic uniaxial anisotropy.…”

New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures

“…[502] This anisotropy of the shape-like behavior can play a significant role in specific materials as it was reported for Lanthanum oxides, where the magnetoelastic interaction contributes to the domain configuration. [21,503] Epitaxially grown perovskite LaFeO 3 thin films possess the in-plane easy axes determined by the substrate: SrTiO 3 imprints its 〈100〉 axis into overlying layer, [503] while La 0.7 Sr 0.3 MnO 3 leads to the appearance of two easy axes 〈110〉 and 〈100〉 in pseudocubic notation. [503] This allows to create planar curvilinear ribbons and observe a highly regular domain pattern in zig-zag geometries, free standing or drawn by a local disruption of the structural and magnetic ordering by Ar + ion implantation, see Figure 11g,h.…”

“…Similar effects are reported for Lanthanum-based oxides islands of different shape imprinted into nonmagnetic matrix. [21] Effects stemming from curvilinear geometries in ferromagnets are often accompanied by the boundary effects, which are active even in planar structures. It is important to develop the respective understanding of the boundary effects also for antiferromagnets to be able to distinguish them from the curvilinear effects and to utilize for applications.…”

“…[14][15][16][17][18] This discussion also tackles the state of the art in modern experimental antiferromagnetism, where the design of the sample topography and boundaries allows to control the domain wall states. [19][20][21][22] With the development of novel fabrication techniques allowing to realize complex 3D architectures, not only the boundary effects but also the extrinsic geometrical properties (e.g., local curvatures) can be addressed rigorously for the case of ferromagnets [23][24][25][26][27] as well as superconductors. [28][29][30] The explored effects are directly related to the interplay between the Traditionally, the primary field, where curvature has been at the heart of research, is the theory of general relativity.…”

Strain-induced Shape Anisotropy in Antiferromagnetic Structures

“…However, initial studies of patterning-induced effects in antiferromagnetic LaFeO 3 could not observe any changes in the domain structure, after patterning different elements with etching [14]. Later studies patterned elements via an Ar + ion implantation-based patterning technique, which resulted in antiferromagnetic structures embedded in a non-magnetic layer [15,16]. This technique led to the observation of changes in the antiferromagnetic ordering near the patterning edge for LaFeO 3 [15,17,18] and more recently La 0.7 Sr 0.3 FeO 3 [16], interpreted as an edge effect near the edge for elements patterned along the easy axis.…”