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

TL;DR

This study uncovers an unusual magnetic ground state in Ca2ScRuO6, a double perovskite ruthenate, revealing ferrimagnetic-like behavior, mixed valence states, and weak antiferromagnetic order with magnetoelastic coupling.

Contribution

It provides the first detailed investigation of the magnetic and structural properties of Ca2ScRuO6, highlighting its complex magnetic ground state and magnetoelastic interactions.

Findings

Ferrimagnetic-like behavior above 40 K

Presence of mixed Ru valence states (Ru5+ and Ru4+)

Weak antiferromagnetic order with reduced magnetic moment

Abstract

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 1.1{\mu}B/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.