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Probing the magnetic ground state and magnetoelastic coupling in double perovskite ruthenate: Ca2ScRuO6

Ruthenates, materials with a single magnetic Ruthenium (Ru) atom, often display an exotic array of ground states ranging from superconductivity to altermagnetism. In this work, we investigated the magnetic ground state of a least explored member of the 4d3 double perovskite ruthenate series A2ScRuO6 (A = Ca, Sr, Ba): Ca2ScRuO6. Interestingly, temperature-dependent bulk susceptibility curve shows ferrimagnetic-like behaviour above the magnetic ordering at around 40 K, which were corroborated by the identification of the mixed valence states, Ru5+ and Ru4+ via X-ray absorption spectroscopy. Structural analysis further revealed atomic-site exchange between the Ru and Sc sites, which results in the Ru mixed valence states. Neutron powder diffraction measurements detected the presence of magnetic Bragg peaks at a low temperature near 4 K and a moderate magnetoelastic coupling near the ordering temperature of 40 K. However, the corresponding symmetry analysis shows a weak Type I antiferromagnetic ground state with a reduced magnetic moment of 1.1μB/Ru atom. Our findings establish an unusual magnetic ground state in the Mott insulating Ca2ScRuO6, where a long range ordered antiferromagnet coexists with small magnetic clusters, which manifests a ferrimagnetic-like high temperature inverse magnetic susceptibility. This system presents a unique platform to study long-range magnetic order in the presence of antisite disorder.