Patrick Woodward, The Ohio State University, The magnetism of double perovskites containing osmium and rhenium

Date: Mon. October 24th, 2016, 12:45 pm-1:45 pm
Location: Rockefeller 221 (Miller Room)
Website: https://research.cbc.osu.edu/woodward.55/

 

Patrick M. Woodward

Department of Chemistry and Biochemistry, The Ohio State University

Over the past several years we have been synthesizing and studying the magnetic properties of A₂MOsO₆ and A₂MReO₆ (Mg, Zn, Cr, Fe, Co, Ni) double perovskites in a quest to understand how the sign and strength of the superexchange interactions change as a function of the relative filling of the 3d and 5d orbitals, as well as the geometry of the crystal structure. In double perovskites where the 5d ion is the only magnetic ion we find that spin-orbit coupling plays a role, even for electron counts like 5d³ where it was assumed to be quenched. Furthermore, the sign and strength of the superexchange coupling between 5d ions is very sensitive to changes in the filling of the 5d orbitals and distortions of the crystal structure. In double perovskites that contain both 3d and 5d ions, differences in the energy levels of the 3d and 5d orbitals causes the 3d−5d superexchange coupling through the e_g orbitals to be insignificant, thereby allowing longer range 5d−5d and 3d−3d superexchange coupling to be competitive. The strength of the competing superexchange interactions can be tuned by changing the filling of d-orbitals and is highly sensitive to changes in chemical pressure. Using these tools we can access magnetic states ranging from ferrimagnetic to antiferromagnetic to spin glasses. The findings of this work have important implications for efforts to design and understand magnetic materials for the 21^st century.