Massachusetts Institute of Technology (MIT), USA
Resonant elastic X-ray scattering (REXS) is a powerful tool to study orderings of spin, charge, and orbital degrees of freedom. I will present our studies on RuO2 and α-Sr2CrO4, by using the REXS technique. (1) Ruthenium oxide (RuO2) has been considered as a Pauli paramagnet. We studied the magnetic ordering of thin films and bulk crystals of rutile RuO2 using resonant magnetic X-ray scattering (RXS) across the Ru-L2 absorption edge and have established the presence and texture of the collinear antiferromagnetic order in RuO2 with TNéel > 300 K. (2) We investigate the electronic ground states of Sr2CrO4, a compound that is a rare embodiment of the spin-1 Kugel-Khomskii model on the square lattice. We have used resonant X-ray diffraction at the Cr-K edge to reveal Néel magnetic order below TN = 112 K, as well as an additional electronic order at the “stripe” wavevector QS = (？; 0) below Ts < 50 K. These findings are examined within the framework of the Kugel-Khomskii model in the mean-field approximation, which supports the stability of the spin Néel phase with subsequent lower-temperature stripe orbital ordering.
Brief CV of Dr.Zhihai Zhu:
Dr. Zhu obtained his Ph. D. in 2016 from the University of Connecticut in the USA, under the advice of Prof. Barrett O. Wells. He currently is a postdoctoral associate at Massachusetts Institute of Technology (MIT) under the direction of Prof. Riccardo Comin. Dr. Zhu’s research lies in correlated-electron physics in transition metal oxides (TMOs). His study is materials and problem based, tackling the full spectrum of a problem from material synthesis (PLD, OMBE) to advanced measurements (Neutron scattering, muon spin rotation, resonant elastic/inelastic x-ray scattering etc.), often at large scale facilities at national labs.