Origin of Magnetism in a Supposedly Nonmagnetic Osmium Oxide

A supposedly nonmagnetic <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>5</a:mn><a:msup><a:mrow><a:mi>d</a:mi></a:mrow><a:mrow><a:mn>1</a:mn></a:mrow></a:msup></a:mrow></a:math> double perovskite oxide is investigated by a combination of spectroscopic and theoretical methods, namely, resonant inelastic x-ray scattering, x-ray absorption spectroscopy, magnetic circular dichroism, and multiplet ligand-field calculations. We found that the large spin-orbit coupling admixes the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mn>5</c:mn><c:mi>d</c:mi></c:math> <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:msub><e:mi>t</e:mi><e:mrow><e:mn>2</e:mn><e:mi>g</e:mi></e:mrow></e:msub></e:math> and <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msub><g:mi>e</g:mi><g:mi>g</g:mi></g:msub></g:math> orbitals, covalency raises the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mn>5</i:mn><i:mi>d</i:mi></i:math> population well above the nominal value, and the local symmetry is lower than <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>O</k:mi><k:mi>h</k:mi></k:msub></k:math>. The obtained electronic interactions account for the finite magnetic moment of Os in this compound and, in general, of <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mn>5</m:mn><m:msup><m:mi>d</m:mi><m:mn>1</m:mn></m:msup></m:math> ions. Our results provide direct evidence of elusive Jahn-Teller distortions, hinting at a strong electron-lattice coupling. Published by the American Physical Society 2024