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Title (deu)
Multipolar Order and Fluctuations in 5d Double Perovskites
Speaker / Lecturer
Bruce Gaulin
McMaster U, Hamilton
Description (deu)

This talk was part of the Workshop on "Spin-Orbit Entangled Quantum Magnetism" held at the ESI September 23 -- 27, 2024.

We have carried out neutron spectroscopic and diffraction studies on powder samples of several 5d families of cubic double perovskites, that involve Os and Re in different oxidation states. This includes 5d3 systems, such as Ba2YOsO6 with Os5+, 5d2 systems such as Ba2MgOsO6 with Os6+, and the 5d1 system Ba2MgReO6 with Re6+. The 5d3 double perovskites all display well defined Neel order with sizeable dipole magnetic moments, while the 5d1 system displays both a structural and a magnetic transition on lowering temperature, consistent with expectations for coupled quadrupolar and dipolar degrees of freedom. The 5d2 cubic double perovskites are particularly intriguing as these display clear phase transitions at T* ~ 45 K where ~ R ln(2) in entropy is released on passing through T*. However, while magnetic inelastic scattering is clearly observed, there is no evidence for the ordering of dipole moments in neutron diffraction, with an upper limit on any possible ordered dipole moment of ~ 0.1 muB. We understand these results in terms of ferro-octupolar order below T*, and argue that this is consistent with the full set of experimental observations on these 5d2 cubic double perovskites. We believe this likely constitutes the first compelling case for octupolar order in a d-orbital Mott insulator.

Keywords (deu)
solid-state magnetismESIcondensed matter physics
Subject (eng)
ÖFOS 2012 -- 103 -- Physics, Astronomy
Type (eng)
Language
[eng]
Persistent identifier
https://phaidra.univie.ac.at/o:2094135
Date created
2024-09-26
Place of creation (eng)
ESI
Duration
36 minutes 36 seconds
Content
Details
Object type
Video
Format
video/mp4
Created
26.09.2024 03:48:09
Metadata