Influence of structure and cation distribution on magnetic anisotropy and damping in Zn/Al doped nickel ferrites
Julia Lumetzberger, Martin Buchner, Santa Pile, V. Ney, Wolfgang Gaderbauer, Niéli Daffé, Marcos V. Moro, Daniel Primetzhofer, K. Lenz, A. Ney
Abstract
An in-depth analysis of Zn/Al-doped nickel ferrites grown by reactive magnetron sputtering is relevant due to their promising characteristics for applications in spintronics. The material is insulating and ferromagnetic at room temperature with an additional low magnetic damping. By studying the complex interplay between strain and cation distribution their impact on the magnetic properties, i.e., anisotropy, damping, and $g$-factor is unravelled. In particular, a strong influence of the lattice site occupation of ${\mathrm{Ni}}_{\text{Td}}^{2+}$ and cation coordination of ${\mathrm{Fe}}_{\text{Oh}}^{2+}$ on the intrinsic damping is found. Furthermore, the critical role of the incorporation of ${\mathrm{Zn}}^{2+}$ and ${\mathrm{Al}}^{3+}$ is evidenced by comparison to a sample of altered composition. Specifically, the dopant ${\mathrm{Zn}}^{2+}$ is evidenced as a tuning factor for ${\mathrm{Ni}}_{\text{Td}}^{2+}$ and therefore unquenched orbital moment directly controlling the $g$-factor. A strain-independent reduction of the magnetic anisotropy and damping by adapting the cation distribution is demonstrated.