X-ray magnetic circular dichroism and photoemission studies of ferromagnetism inCaMn1−xRuxO3thin films

We have studied the electronic and magnetic properties of epitaxially grown ${\text{CaMn}}_{1\ensuremath{-}x}{\text{Ru}}_{x}{\text{O}}_{3}$ thin films $(x=1.0,0.75,0.5)$ by soft x-ray absorption, soft x-ray magnetic circular dichroism (XMCD), and hard x-ray photoemission spectroscopy (HXPES) measurements. The XMCD studies indicated that the spin moments of Mn and Ru are aligned in opposite directions. The valence-band HXPES spectra revealed that the $\text{Ru}\text{ }4d$ ${t}_{2g}$ states around the Fermi level and the $\text{Mn}\text{ }3d$ ${t}_{2g}$ up-spin states centered $\ensuremath{\sim}2\text{ }\text{eV}$ below it showed systematic concentration dependences. From these results, we propose that the localized $\text{Mn}\text{ }3d$ ${t}_{2g}$ states and the itinerant $\text{Ru}\text{ }4d$ ${t}_{2g}$ band are antiferromagnetically coupled and give rise to the ferromagnetic ordering, which is in analogy to the mechanism proposed for double perovskite oxides, such as ${\text{Sr}}_{2}{\text{FeMoO}}_{6}$.