Distinct pressure evolution of coupled nematic and magnetic orders in FeSe

Böhmer, A.E. and Kothapalli, K. and Jayasekara, W.T. and Wilde, J.M. and Li, B. and Sapkota, A. and Ueland, B.G. and Das, P. and Xiao, Y. and Bi, W. and Zhao, J. and Alp, E.E. and Bud'Ko, S.L. and Canfield, P.C. and Goldman, A.I. and Kreyssig, A.

Volume: 100 Pages:
DOI: 10.1103/PhysRevB.100.064515
Published: 2019

We present a microscopic study of nematicity and magnetism in FeSe over a wide temperature and pressure range using high-energy x-ray diffraction and time-domain Mössbauer spectroscopy. The low-temperature magnetic hyperfine field increases monotonically up to ∼6 GPa. The orthorhombic distortion initially decreases under increasing pressure but is stabilized at intermediate pressures by cooperative coupling to the pressure-induced magnetic order. Close to the reported maximum of the superconducting critical temperature at p=6.8GPa, the orthorhombic distortion suddenly disappears and a new tetragonal magnetic phase occurs. The pressure and temperature evolution of the structural and magnetic order parameters suggests that they have distinct origins. © 2019 American Physical Society.

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