Shape-imposed anisotropy in antiferromagnetic complex oxide nanostructures

Abstract

In this study, we report on a shape-imposed magnetic anisotropy in micro-and nanostructures defined in antiferromagnetic (AF) LaFeO3 (LFO) thin films. Two distinct types of structures are investigated; embedded magnets created via ion implantation, and free-standing magnets created via ion milling. Using a combination of x-ray photoemission electron microscopy and x-ray absorption spectroscopy, we examine the impact of structure type, AF layer thickness, and crystal geometry on the Néel vector orientation in these structures. We demonstrate a distinct shape-imposed anisotropy in embedded and free-standing structures alike, and show that both parallel and perpendicular alignment of the AF spin axis with respect to structure edges can be achieved by variation of the AF layer thickness and the orientation of the structure edges with respect to the LFO crystalline axes. This work demonstrates how fabrication procedure affects the magnetic order in thin film AF nanostructures and shows how nanoscale patterning can be used to control the orientation of the Néel vector in epitaxial oxide thin films.

Domain-wall orientation in antiferromagnets controlled by magnetoelastic effects

“…The previous system is integrated over a computational square domain of side 2L = 500 nm which, according to the above parameter set, is much larger than the domain wall width x DW = 31.6 nm, in line with the assumption made in Section 2. We also used (8) conditions at the vertical edges x = ±L. On the other hand, at the horizontal edges y = ±L, having normal q = ±e y , we implemented the following piecewise conditions:…”

“…Magnetoelastic effects are usually neglected while considering antiferromagnetic dynamics and switching. However, they can pin the domain walls [1], modify magnon spectra [2][3][4], stabilise antiferromagnetic textures in the finite size samples [5][6][7][8][9][10]. As such, magnetoelastic effects play an important role in the dynamics of antiferromagnets and with the proper tailoring can even open new functionalities.…”

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

“…[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. [19,20] The domains are arranged with respect to the ribbon period. The orientation of the Néel vector is determined by the surrounding.…”

“…[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.…”

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

“…[23,24] However, shape anisotropy effects are theoretically predicted to result from magnetoelastic forces and surface magnetic anisotropy, [25,26] and have indeed been observed in in single-crystalline NiO/Fe and CoO/Fe discs through imprinting from the FM Fe layer [27] as well as La 1-x Sr x FeO 3 and La 1-x Sr x FeO 3 /LSMO micro-/nanoscale features that were defined using an Ar + ion implantation-based patterning technique. [17,21,[28][29][30][31][32][33][34] This technique results in magnetic islands embedded within a non-magnetic matrix, and it is postulated that these edge effects result from a lateral compressive strain imposed onto the magnetic islands from the surrounding matrix. [35] Soft x-ray photoemission electron microscopy (X-PEEM) remains one of the few imaging techniques capable of directly imaging AFM domains in thin films by taking advantage of the x-ray magnetic linear dichroism (XMLD) effect.…”