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arXiv · 1906.10974

Room-temperature insulating ferromagnetic (Ni,Co)1+2xTi1-xO3 thin films

Yukari Fujioka·Johannes Frantti·Christopher Rouleau·Alexander Puretzky·Zheng Gai·Nickolay Lavrik·Andreas Herklotz·Ilia N. Ivanov·Harry M. Meyer
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Abstract

Insulating uniaxial room-temperature ferromagnets are a prerequisite for commonplace spin wave-based devices, the obstacle in contemporary ferromagnets being the coupling of ferromagnetism with large conductivity. We show that the uniaxial $A^{1+2x}$Ti$^{4+}$$_{1-x}$O$_3$ (ATO), $A=$Ni$^{2+}$,Co$^{2+}$ and $0.6<x \leq 1$, thin films are electrically insulating ferromagnets already at room-temperature. The octahedra network of the ATO and ilmenite structures are similar yet different octahedra-filling proved to be a route to switch from the antiferromagnetic to ferromagnetic regime. Octahedra can continuously be filled up to $x=1$, or vacated $(-0.24<x<0)$ in the ATO structure. TiO-layers, which separate the ferromagnetic (Ni,Co)O-layers and intermediate the antiferromagnetic coupling between the ferromagnetic layers in the NiTiO$_3$ and CoTiO$_3$ ilmenites, can continuously be replaced by (Ni,Co)O-layers to convert the ATO-films to ferromagnetic insulator with abundant direct cation interactions.

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Yukari Fujioka, Johannes Frantti, Christopher Rouleau, Alexander Puretzky, Zheng Gai, Nickolay Lavrik, Andreas Herklotz, Ilia N. Ivanov, Harry M. Meyer. 2019-07-07. Room-temperature insulating ferromagnetic (Ni,Co)1+2xTi1-xO3 thin films. https://doi.org/10.1002/andp.201900299

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