Spin Gap and the Nature of the 4d3 Magnetic Ground State in the Frustrated FCC Antiferromagnet Ba2YRuO6

TL;DR

This study investigates the magnetic properties of Ba2YRuO6, revealing a spin gap and spin wave behavior that challenge expectations based on its large Curie-Weiss temperature, highlighting the role of spin-orbit coupling in 4d systems.

Contribution

The paper provides the first neutron spectroscopy analysis of Ba2YRuO6, identifying a spin gap and detailed spin wave spectrum, and compares these findings with related 4d materials to understand spin-orbit effects.

Findings

A 5 meV spin gap develops below T_N=36K.

Spin waves extend up to 14 meV with a small bandwidth.

The results suggest strong spin-orbit coupling influences in 4d magnetic systems.

Abstract

The geometrically frustrated double perovskite Ba2YRuO6 has magnetic 4d3 Ru5+ ions decorating an undistorted face-centered cubic (FCC) lattice. This material has been previously reported to exhibit commensurate long-range antiferromagnetic order below T_N = 36K, a factor f = 15 times lower than its Curie-Weiss temperature Theta_CW = -522 K, and purported short-range order to T* = 47K. We report new time-of-flight neutron spectroscopy of Ba2YRuO6 which shows the development of a 5 meV spin gap in the vicinity of the [100] magnetic ordering wavevector below T_N = 36K, with the transition to long-range order occurring at T* = 47K. We also report spin waves extending to 14 meV, a surprisingly small bandwidth in light of the large Theta_CW. We compare the spin gap and bandwidth to relevant neutron studies of the isostructural 4d1 material Ba2YMoO6,and discuss the results in the framework of relatively strong spin-orbit coupling expected in 4d magnetic systems.