Multipolar Order and Fluctuations in 5d Double Perovskites

Explore neutron spectroscopic and diffraction studies on powder samples of 5d cubic double perovskites involving Os and Re in various oxidation states. Delve into the magnetic behavior of 5d3, 5d2, and 5d1 systems, including Ba2YOsO6, Ba2MgOsO6, and Ba2MgReO6. Examine the well-defined Neel order in 5d3 double perovskites, the coupled quadrupolar and dipolar degrees of freedom in 5d1 systems, and the intriguing phase transitions in 5d2 cubic double perovskites. Investigate the evidence for ferro-octupolar order below T* in 5d2 systems, potentially representing the first compelling case for octupolar order in a d-orbital Mott insulator. Gain insights into the experimental observations and their implications for understanding multipolar order and fluctuations in these complex materials.