Abstract
We report time-of-flight neutron spectroscopy and neutron and x-ray diffraction studies of the 5d2 double perovskite magnets, Ba2MOsO6 (M=Zn,Mg,Ca). These materials host antiferromagnetically coupled 5d2 Os6+ ions decorating a face-centered cubic (fcc) lattice and are found to remain cubic down to the lowest temperatures. They all exhibit thermodynamic anomalies consistent with a single phase transition at a temperature T∗, and a gapped magnetic excitation spectrum with spectral weight concentrated at wave vectors typical of type-I antiferromagnetic orders. However, while muon spin resonance experiments show clear evidence for time-reversal symmetry breaking below T∗, we observe no corresponding magnetic Bragg scattering signal. These results are shown to be consistent with ferro-octupolar symmetry breaking below T∗, and are discussed in the context of other 5d double perovskite magnets and theories of exotic orders driven by multipolar interactions.
| Original language | English |
|---|---|
| Article number | 087206 |
| Journal | Physical Review Letters |
| Volume | 124 |
| Issue number | 8 |
| DOIs | |
| State | Published - Feb 27 2020 |
Funding
This work was supported by the Natural Sciences and Engineering Research Council of Canada. It was also 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 G.\u2009M. Luke and G. Chen. We are very grateful for the instrument and sample environment support provided during our inelastic neutron scattering measurements at SEQUOIA. The experiments which were performed at the Spallation Neutron Source at Oak Ridge National Laboratory were sponsored by the U.S. Department of Energy, Office of the Basic Energy Sciences, Scientific User Facilities Division. The authors would also like to acknowledge ILL for beam time allocation experiment code 5-31-2577. We acknowledge the BL04-MSPD staff of ALBA for the x-ray synchrotron powder diffraction data collection.