Fully filling-controlled pyrochlore ruthenates: emergent ferromagnetic-metal state and geometrical Hall effect

Ryoma Kaneko; Kentaro Ueda; Shiro Sakai; Yusuke Nomura; Marie-Therese Huebsch; Ryotaro Arita; Yoshinori Tokura

doi:10.1103/PhysRevB.103.L201111

paper

Fully filling-controlled pyrochlore ruthenates: emergent ferromagnetic-metal state and geometrical Hall effect

arXiv:2103.04360 · doi:10.1103/PhysRevB.103.L201111

Abstract

Carrier doping to the Mott insulator is essential to produce highly correlated metals with emergent properties. Pyrochlore ruthenates, Pr $_{2}$ Ru $_{2}$ O $_{7}$ (Ru- $4 d$ electron number, $n = 4$ ) and Ca $_{2}$ Ru $_{2}$ O $_{7}$ ( $n = 3$ ), are a Mott insulator and a magnetic bad metal, respectively, due to the strong electron correlation. We investigate magneto-transport properties of (Pr $_{1 - x}$ Ca $_{x}$ ) $_{2}$ Ru $_{2}$ O $_{7}$ in a whole band-filling range, $0 < x < 1$ . With increasing hole-doping $x$ , the system undergoes an insulator-metal transition. When Ca $_{2}$ Ru $_{2}$ O $_{7}$ is doped with electrons ( $0.5 < x < 0.9$ ), the enhanced coupling among Ru- $4 d$ spins produces a ferromagnetic-metal phase with a large anomalous-Hall angle up to 2 %. We discuss the electronic phase transitions in (Pr $_{1 - x}$ Ca $_{x}$ ) $_{2}$ Ru $_{2}$ O $_{7}$ in view of Hund's metal.

6 pages, 4 figures