We report on the structural, magnetic, and electronic properties of two new double-perovskites synthesized under high pressure; Pb2CaOsO6 and Pb2ZnOsO6. Upon cooling below 80 K, Pb2CaOsO6 simultaneously undergoes a metal--insulator transition and develops antiferromagnetic order. Pb2ZnOsO6, on the other hand, remains a paramagnetic metal down to 2 K. The key difference between the two compounds lies in their crystal structure. The Os atoms in Pb2ZnOsO6 are arranged on an approximately face-centred cubic lattice with strong antiferromagnetic nearest-neighbor exchange couplings. The geometrical frustration inherent to this lattice prevents magnetic order from forming down to the lowest temperatures. In contrast, the unit cell of Pb2CaOsO6 is heavily distorted up to at least 500 K, including antiferroelectric-like displacements of the Pb and O atoms despite metallic conductivity above 80 K. This distortion relieves the magnetic frustration, facilitating magnetic order which in turn drives the metal--insulator transition. Our results suggest that the phase transition in Pb2CaOsO6 is spin-driven, and could be a rare example of a Slater transition.
@article{arxiv.2009.04196,
title = {Magnetically induced metal-insulator transition in Pb2CaOsO6},
author = {Henrik Jacobsen and Hai L. Feng and Andrew J. Princep and Marein C. Rahn and Yanfeng Guo and Jie Chen and Yoshitaka Matsushita and Yoshihiro Tsujimoto and Masahiro Nagao and Dmitry Khalyavin and Pascal Manuel and Claire A. Murray and Christian Donnerer and James G. Vale and Marco Moretti Sala and Kazunari Yamaura and Andrew T. Boothroyd},
journal= {arXiv preprint arXiv:2009.04196},
year = {2021}
}
Comments
14 pages, 9 figures. Accepted as a regular article in Phys. Rev. B