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arXiv · 1906.10975

In Quest of a Ferromagnetic Insulator -- Structure Controlled Magnetism in Mg-Ti-O Thin Films

Johannes Frantti·Yukari Fujioka·Christopher Rouleau·Alexandra Steffen·Alexander Puretzky·Nickolay Lavrik·Ilia N. Ivanov·Harry M. Meyer
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Abstract

Ferromagnetic insulator thin films can convey information by spin waves, avoiding charge displacement and Eddy current losses. The sparsity of high-temperature insulating ferromagnetic materials hinders the development of spin wave based devices. Stoichiometric magnesium titanate, MgTiO$_3$, has an electronic-energy-band structure in which all bands are either full or empty, being a paramagnetic insulator. The MgTiO$_3$ ilmenite consists of ordered octahedra and cation network in which one third of the octahedra are vacant, one third host magnesium and one third titanium. By giving up these characteristics, a rich variety of different magnetic structures can be formed. Our experiments and electronic-energy-band-structure computations show that the magnetic and electric properties of Mg-Ti-O films can drastically be changed and controlled by Mg- and Ti-cation arrangement and abundancy in the octahedra. Insulating titanium- and semiconducting magnesium-rich films were ferromagnetic up to elevated temperatures. The presence and origin of ferromagnetic insulating phase in the films is not apparent - the expectation, based on the well-established rules set by Goodenough and Kanamori, is paramagnetic or antiferromagnetic ordering. We show that ferro- and paramagnetic phases, possessing the same stoichiometry, can be obtained by merely rearranging the cations, thus allowing defect-free interfaces in multilayer structures.

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Johannes Frantti, Yukari Fujioka, Christopher Rouleau, Alexandra Steffen, Alexander Puretzky, Nickolay Lavrik, Ilia N. Ivanov, Harry M. Meyer. 2019-06-26. In Quest of a Ferromagnetic Insulator -- Structure Controlled Magnetism in Mg-Ti-O Thin Films. https://doi.org/10.1021/acs.jpcc.9b05189

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