Magnetic moments of W $5d$ in ${\mathrm{Ca}}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ and ${\mathrm{Sr}}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ double perovskites

We have investigated the magnetic moment of the W ion in the ferrimagnetic double perovskites ${\mathrm{Sr}}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ and ${\mathrm{Ca}}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ by x-ray magnetic circular dichroism at the W $L_{2,3}$ edges. In both compounds a finite negative spin and positive orbital magnetic moment was detected. The experimental results are in good agreement with band-structure calculations for ${(\mathrm{Sr}∕\mathrm{Ca})}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ using the full-potential linear muffin-tin orbital method. It is remarkable that the magnetic ordering temperature, $T_{\mathrm{C}}$, is correlated with the magnetic moment at the “nonmagnetic” W atom.

Figure 1

(Color online) Orbital resolved density of states (DOS) of ${\mathrm{Sr}}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ with spin-orbit coupling. The Fermi energy is indicated by zero energy level.

Figure 2

(Color online) XANES spectra and derived XMCD spectra for ${\mathrm{Sr}}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ (upper panel) and ${\mathrm{Ca}}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ (lower panel). The XANES spectra (symbols) are corrected as described in the text. The XMCD spectra are shown as full lines. The XMCD spectrum of the W $L_3$ edge was multiplied by a factor of 7 for ${\mathrm{Sr}}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ and by a factor of 3 for ${\mathrm{Ca}}_2\mathrm{Cr}\mathrm{W}{\mathrm{O}}_6$ for clarity.