Abstract
Time-of-flight inelastic neutron scattering measurements have been carried out on polycrystalline samples of the 4d3 and 5d3 double pervoskite antiferromagnets La2LiRuO6 and La2LiOsO6. These reveal the development of an inelastic spin gap in La2LiRuO6 and La2LiOsO6 of ∼1.8(8) and 6(1) meV, below their respective ordering temperatures TN,∼23.8 and 30 K. The bandwidths of the spin excitations are shown to be ∼5.7(9)and12(1)meV, respectively, at low temperatures. Spin gaps are surprising in such magnets as the t2g levels of Ru5+ or Os5+ are expected to be half-filled, resulting in an anticipated orbital singlet for both materials. We compare these results in monoclinic double perovskites La2LiRuO6 and La2LiOsO6 with those in cubic Ba2YRuO6 and Ba2YOsO6 as well as with those in other monoclinic La2NaRuO6,La2NaOsO6, and Sr2ScOsO6 and model the inelastic magnetic scattering with linear spin-wave theory using minimal anisotropic exchange interactions. We discuss the possible role of the distortion of the face-centered-cubic double perovskite structure on the spin gap formation and geometric frustration in these materials and show that TN scales with the top of the spin-wave band in all members of these families that display long-range order.
Original language | English |
---|---|
Article number | 104434 |
Journal | Physical Review B |
Volume | 98 |
Issue number | 10 |
DOIs | |
State | Published - Sep 28 2018 |
Funding
Research at McMaster University was supported by NSERC of Canada. This work was supported, in part, by the National Science Foundation under Grant No. PHYS-1066293 and the hospitality of the Aspen Center for Physics. We also acknowledge the hospitality of the Telluride Science Research Center. We gratefully acknowledge useful conversations with A. Taylor, R. F. Fishman, and S. Calder. We are very grateful for the instrument and sample environment support provided during our INS experiment at SEQUOIA. The experiment which was performed at the Spallation Neutron Source at Oak Ridge National Laboratory was sponsored by the U.S. Department of Energy, Office of the Basic Energy Sciences, Scientific User Facilities Division.