Modification of magnetocrystalline anisotropy via ion-implantation

Michael S Lee,Elke Arenholz,Yayoi Takamura,Rajesh V Chopdekar,Padraic Shafer

doi:10.1063/1.5134867

Abstract

The ability to systematically modify the magnetic properties of epitaxial La0.7Sr0.3MnO3 thin films is demonstrated through the use of Ar+ ion implantation. With increasing implant dose, a uniaxial expansion of the c-axis of the unit cell leads to a transition from in-plane toward perpendicular magnetic anisotropy. Above a critical dose of 3 × 1013 Ar+/cm2, significant crystalline disorder exists leading to a decrease in the average Mn valence state and near complete suppression of magnetization. Combined with lithographic techniques, ion implantation enables the fabrication of magnetic spin textures consisting of adjacent regions with tunable magnetic anisotropy in complex oxide thin films.

Highlights

Fine control of magnetocrystalline anisotropy is critical for improvements in technologies dependent on magnetic thin films with perpendicular magnetic anisotropy (PMA), such as hard disk drives, and will be necessary for future magnetic devices based on spin textures
When LSMO is grown under tensile or slightly compressive strain on SrTiO3 [STO, ratio of c- to a-lattice parameters (c/a ratio) = 0.987] or (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT, c/a ratio = 1.007) substrates, respectively, the magnetic moments prefer to lie within the film plane but switch to out-ofplane under large compressive strain imposed by LaAlO3 (LAO, c/a ratio = 1.053)
PMA emerging for x > 0.5.10 These studies demonstrate the potential for designing the magnetocrystalline anisotropy but require specific interfaces or substrate selection that cannot be readily modified on the scale of magnetic device features

Summary

Introduction

Fine control of magnetocrystalline anisotropy is critical for improvements in technologies dependent on magnetic thin films with perpendicular magnetic anisotropy (PMA), such as hard disk drives, and will be necessary for future magnetic devices based on spin textures.1–3 Artificial magnetic skyrmions are one such example, but their fabrication can require lithographically defined, multilayer structures to form adjacent regions of both in-plane and outof-plane moments.4–8 The ability to modulate magnetocrystalline anisotropy within a single film would streamline device processing and minimize the complexity of introducing additional interfaces. The AD film shows the expected XA/XMCD spectral shape for LSMO with mixed Mn3+/Mn4+ ions, which leads to robust magnetic properties through the double exchange mechanism.25,26 The XA/XMCD spectral shapes remain unchanged as the dose increases to a critical dose of 3 × 1013 Ar/cm2 above which additional features begin to emerge at the low energy side of the L3 peak, indicating changes in the average Mn valence state.

Results

Conclusion