Designing Magnetic Anisotropy through Strain Doping

• Published in: Advanced science 2018-11, Vol.5 (11), p.1800356-n/a
• Main Authors: Herklotz, Andreas, Gai, Zheng, Sharma, Yogesh, Huon, Amanda, Rus, Stefania F., Sun, Lu, Shen, Jian, Rack, Philip D., Ward, Thomas Z.
• Format: Article
• Language: English
• Subjects: Anisotropy; Communication; Communications; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Energy; epitaxy; implantation; Ion implantation; magnetism; MATERIALS SCIENCE; Microscopy; Public access; R&D; Research & development; Semiconductors; spin orbit coupling; strain; Symmetry
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.201800356

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. Helium atoms push magnetic control in crystalline films. Implanting He atoms into a magnetic crystal provides a means of controlling lattice symmetry and the ease with which magnetic spins align to applied magnetic fields. Designer multiscale controllable spin anisotropy is demonstrated in a spinel CoFe2O4 epitaxial film.