Tuning Perpendicular Magnetic Anisotropy by Oxygen Octahedral Rotations in $({\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3)/({\mathrm{SrIrO}}_3)$ Superlattices

Perpendicular magnetic anisotropy (PMA) plays a critical role in the development of spintronics, thereby demanding new strategies to control PMA. Here we demonstrate a conceptually new type of interface induced PMA that is controlled by oxygen octahedral rotation. In superlattices comprised of ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ and ${\mathrm{SrIrO}}_3$, we find that all superlattices ($0\le x\le 1$) exhibit ferromagnetism despite the fact that ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ is antiferromagnetic for $x>0.5$. PMA as high as $4\times {10}^6{\mathrm{erg}/\mathrm{cm}}^3$ is observed by increasing $x$ and attributed to a decrease of oxygen octahedral rotation at interfaces. We also demonstrate that oxygen octahedral deformation cannot explain the trend in PMA. These results reveal a new degree of freedom to control PMA, enabling discovery of emergent magnetic textures and topological phenomena.

Figure 1

Ferromagnetism in SLs. (a) Temperature dependence of magnetization for SLs. (b) XMCD spectra of SLs ($x=0$) at both the Mn and Ir $L_{2,3}$ edges measured under the same experimental conditions.

Figure 2

Perpendicular magnetic anisotropy in SLs. (a)–(c) Magnetic hysteresis loops along in-plane (IP) and out-of-plane (OOP) directions of SLs with (a) $x=1$, (b) $x=0.8$, and (c) $x=0.5$. (d) The $x$ dependence of normalized remnant magnetizations along IP and OOP directions. (e) Comparison of $x$ dependence of PMA constant ($K_{\mathrm{eff}}$) and mean tetragonal distortion ($c/a$).

Figure 3

Oxygen octahedral deformation in SLs. (a) Sketch of the correlation between XLD and OOD. (b),(c) XLD spectra of SLs and reference (${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3$ and ${\mathrm{SrIrO}}_3$) films at the Mn and Ir $L_{2,3}$ edges at room temperature. (d) Sketch of OOD in SLs.

Figure 4

Oxygen octahedral rotation in SLs. (a) L scan along (00L) crystal truncation rod for a SL ($x=0.5$). (b) Sketch of OOR geometry in SLs. (c) Normalized ($1/2$, $1/2$, $3/2$) peaks for SLs with different $x$. Intensity is normalized by the corresponding (002) Bragg peak. (d) Comparison of the $x$ dependence of PMA ($K_{\mathrm{eff}}$) and OOR.