2024/05/08 by Gen, Masaki, Nakajima, Taro, Saito, Hiraku +2
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.2405.05108
We report low-temperature powder X-ray and neutron diffraction studies on breathing pyrochlore magnets CuMCr4S8 (M = Al, Ga), which undergo a magnetic transition at T\rm N ≈ 21 and 31 K for M = Al and Ga, respectively. X-ray diffraction reveals that the magnetic transition accompanies a structural transition from cubic F 43m to polar orthorhombic Imm2 symmetry for both the compounds, with larger distortion observed for M = Ga at low temperatures. Neutron diffraction reveals incommensurate magnetic modulation \mathbf Q = (q\rm IC, 0.5, 0) in the orthorhombic setting, where q\rm IC ≈ 0.39 and 0.31 for M = Al and Ga, respectively. Our magnetic-structure analysis suggests cycloid-type magnetic order but not proper-screw type for both the compounds. We find strong correlation between the local spin configuration and Cr-Cr bond lengths, indicating that the spin-lattice coupling as well as the magnetic frustration play an important role in determining the ground state. CuMCr4S8 potentially offers a platform to explore magnetoelectric effects arising from the helimagnet driven electric polarity.