Spin-lattice coupling across the singular magnetostructural transition in $\mathrm{P}{\mathrm{r}}_{0.5}\mathrm{S}{\mathrm{r}}_{0.5}\mathrm{Co}{\mathrm{O}}_3$ by x-ray magnetic circular dichroism

We have performed temperature-dependent x-ray magnetic circular dichroism on ferromagnetic $\mathrm{P}{\mathrm{r}}_{0.5}\mathrm{S}{\mathrm{r}}_{0.5}\mathrm{Co}{\mathrm{O}}_3$ at the $\mathrm{Co}{L}_{2,3}$ edges to analyze the correlation of the spin and orbital angular components of the magnetization with the singular magnetostructural anomalies at ∼120 K. We found a sizable orbital angular momentum in Co atoms that follows a temperature dependence very similar to that of the spin momentum. Their sum agrees with the bulk magnetization. Taken together with recent x-ray absorption spectra showing the absence of changes in the electronic filling of Co $3d$ states across the magnetostructural transition, our results demonstrate the relevance of the spin-orbit coupling for the stabilization of two distinct ferromagnetic phases in this metallic perovskite. The Co spin-state model is discussed on the basis of charge-transfer multiplet calculations of the dichroic spectral shape.

Figure 1

(a) ac susceptibility $(H=10\mathrm{Oe},f=13\mathrm{Hz}$) measured in PSCO using a dc field of 75 Oe (FC). (b) Magnetization versus zero-field cooling (ZFC) in FM1, FM2, and paramagnetic phases. (c) Temperature dependence of the magnetization (FC) measured at 100, 200, 400, and 1000 Oe.

Figure 2

(a) $\mathrm{Co}{L}_{2,3}$ x-ray absorption spectra with positive ($I^{+}$, open black circles) and negative ($I^{-}$, open red circles) helicities in $\mathrm{P}{\mathrm{r}}_{0.50}\mathrm{S}{\mathrm{r}}_{0.50}\mathrm{Co}{\mathrm{O}}_3$ at 50 K and a 5 T applied field. (b) XMCD signal (solid black line, left axis) and the corresponding XMCD integration applied in sum-rules calculations (dotted line, right axis). (c) Temperature dependence of the $\mathrm{Co}{L}_{2,3}$ XMCD signal at 0.1 T. The spectra have been vertically shifted for clarity.

Figure 3

(a) Temperature dependence of the spin magnetic moment $m_{\mathrm{S}}$ (solid black circles) and the orbital magnetic moment $m_{\mathrm{L}}$ (solid blue triangles) derived from XMCD spectra of PSCO at 0.1 T. The inset: coercive field $\left({\mu }_0{H}_{\mathrm{C}}\right)$ versus temperature. (b) Temperature dependence of $m_{\mathrm{L}}+m_{\mathrm{S}}$ (solid black triangles) and dc magnetization (open blue circles) measured at 0.1 T. The solid red line is a guide to the eye. The shape of $\mathrm{Co}{\mathrm{O}}_6$ octahedra in each structural phase is schematically represented.

Figure 4

(From top to bottom) Experimental XMCD spectra (solid blue line) on $\mathrm{P}{\mathrm{r}}_{0.50}\mathrm{S}{\mathrm{r}}_{0.50}\mathrm{Co}{\mathrm{O}}_3$ at 50 K under an applied magnetic field of 5 T and weighted addition of CTM calculations (solid black lines) to build model one, model two, and model three (see the text for a description).