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 |
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Article number | 087206 |
Journal | Physical Review Letters |
Volume | 124 |
Issue number | 8 |
DOIs | |
State | Published - Feb 27 2020 |