Designing Magnetic Anisotropy through Strain Doping.

Andreas Herklotz,Lu Sun,Stefania F Rus,Jian Shen,Zheng Gai,Thomas Z Ward,Amanda Huon,Yogesh Sharma,Philip D Rack

doi:10.1002/advs.201800356

Abstract

The coupling between a material's lattice and its underlying spin state links structural deformation to magnetic properties; however, traditional strain engineering does not allow the continuous, post‐synthesis control of lattice symmetry needed to fully utilize this fundamental coupling in device design. Uniaxial lattice expansion induced by post‐synthesis low energy helium ion implantation is shown to provide a means of bypassing these limitations. Magnetocrystalline energy calculations can be used a priori to estimate the predictive design of a material's preferred magnetic spin orientation. The efficacy of this approach is experimentally confirmed in a spinel CoFe2O4 model system where the epitaxial film's magnetic easy axis is continuously manipulated between the out‐of‐plane (oop) and in‐plane (ip) directions as lattice tetragonality moves from ip to oop with increasing strain doping. Macroscopically gradual and microscopically abrupt changes to preferential spin orientation are demonstrated by combining ion irradiation with simple beam masking and lithographic procedures. The ability to design magnetic spin orientations across multiple length scales in a single crystal wafer using only crystal symmetry considerations provides a clear path toward the rational design of spin transfer, magnetoelectric, and skyrmion‐based applications where magnetocrystalline energy must be dictated across multiple length scales.

Highlights

The coupling between a material’s lattice and its underlying spin state links structural deformation to magnetic properties; traditional strain method of tuning spin orientation in crystalline materials is by exploiting magnetostriction and shape anisotropy engineering does not allow the continuous, post-synthesis control of lattice effects
The ability to design magnetic spin orientations across multiple length scales in a single crystal wafer using only crystal symmetry considerations provides a clear path toward the rational design of spin transfer, magnetoelectric, and skyrmion-based was shown to be a viable means of strain doping epitaxial oxide films by inducing single-axis out-of-plane lattice expansion while leaving the in-plane axes epitaxially locked to the underlying subapplications where magnetocrystalline energy must be dictated across strate.[10,11,12]
Possible to continuously tune across a full range of magnetic anisotropies in epitaxial magnetic spinel films post growth. This is accomplished by exposing CoFe2O4 films Control of spin orientation in crystalline materials is critical to to low energy He ion implantation which drives uniaxial oop fundamental and applied efforts related to magnetoelectrics,[1] lattice expansion, thereby changing the magnetoelastic energies spin transport,[2,3] and skyrmion dynamics.[4,5]

Summary

Introduction

The coupling between a material’s lattice and its underlying spin state links structural deformation to magnetic properties; traditional strain method of tuning spin orientation in crystalline materials is by exploiting magnetostriction and shape anisotropy engineering does not allow the continuous, post-synthesis control of lattice effects.

Results

Conclusion