Spin reorientation in Dy-based high-entropy oxide perovskite thin films

We present a study on the structural and magnetic properties of thin films of the high entropy perovskite $\mathrm{Dy}\left({\mathrm{Fe}}_{0.2}{\mathrm{Mn}}_{0.2}{\mathrm{Co}}_{0.2}{\mathrm{Cr}}_{0.2}{\mathrm{Ni}}_{0.2}\right){\mathrm{O}}_3$ (Dy5BO). An element-sensitive investigation was performed using synchrotron-based x-ray absorption spectroscopy, employing x-ray magnetic circular and linear dichroism. The results reveal that the moments residing on the $3d$ transition metal ions and the rare-earth $\mathrm{Dy}$ ions produce a saturation magnetization one order of magnitude larger than any previously studied high-entropy oxide perovskite. Employing temperature-dependent x-ray magnetic linear dichroism, we see clear features of a spin reorientation at the $\mathrm{Mn}$ and $\mathrm{Fe}$ sites, occurring around 18 K, likely driven by the interaction of the corresponding transition metal ions and $\mathrm{Dy}$.

Figure 1

(a) XRD $\theta \text{−}2\theta$ scan of a 12 nm thick $\mathrm{Dy}5B\mathrm{O}$ film grown on a (001)-oriented STO substrate. The film displays good crystal quality without any secondary phases. (b) STEM image of the film along the [100] direction, showing epitaxial growth. (c) EDX images recorded in the same area as (b), revealing an isotropic and random distribution of the transition metal elements.

Figure 2

SQUID-VSM magnetic hysteresis loops measured at different temperature on a 12 nm thick $\mathrm{Dy}5B\mathrm{O}$ film, with (a) an in-plane magnetic film and (b) an out-of-plane magnetic field.

Figure 3

XAS spectra (upper panel) and XMCD spectra (lower panel) of (a) $\mathrm{Ni}$, (b) $\mathrm{Mn}$, (c) $\mathrm{Fe}$, (d) $\mathrm{Co},$ and (e) $\mathrm{Cr}$ recorded at 2.5 K. The measurements are conducted in the out-of-plane geometry with a 6 T field.

Figure 4

XMCD loops collected at the ${\mathrm{L}}_3$ edge of the transition metal elements in the $5B$ block of the $\mathrm{Dy}5B\mathrm{O}$ film. The loops were collected at 2.5 K and 25 K, in both the grazing and out-of-plane geometry by sweeping the magnetic field between $-6$ T and 6 T in 0.1 T steps.

Figure 5

(a) Measurement geometry for the recording of XMLD spectra. The incident angle of x-rays is $\mathrm{\Theta }={30}^{\circ }$. (b) Normalized XAS spectra recorded with $s$- and $p$-polarized x-rays. (c) XMLD spectrum (blue curve) obtained at 2.5 K at the Fe ${\mathrm{L}}_2$ edge. Panels (d)–(h) show the trend with temperature of the XMLD ${\mathrm{L}}_2$ peaks C and D, respectively, for (d) $\mathrm{Fe}$, (e) $\mathrm{Ni}$, (f) $\mathrm{Mn}$, (g) $\mathrm{Co},$ and (h) $\mathrm{Cr}$. The spectra are obtained at zero-field conditions.

Figure 6

XMCD hysteresis loops collected at the ${\mathrm{M}}_5$ edge of $\mathrm{Dy}$. The loops recorded at 2.5 K and 18 K in both (a) the grazing and (b) out-of-plane x-ray geometry.