PdCrO₂ under uniaxial pressure: Incommensurate-to-incommensurate transition

Nina Stilkerich^1,2, Tobias Ritschel¹, Seunghyun Khim², Andrew P. Mackenzie^2,3, Jochen Geck¹, and Clifford W. Hicks^2,4
1 Institut für Festkörper- und Materialphysik, Technische Universität Dresden, Germany
2 Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
3 School of Physics and Astronomy, University of St. Andrews, United Kingdom
4 School of Physics and Astronomy, University of Birmingham, United Kingdom

PdCrO₂ is a frustrated antiferromagnet on a triangular lattice. The unstressed compound is believed to exhibit a double-q magnetic structure below its Néel temperature at 37.5K. Using uniaxial pressure, the frustration can be altered: When compressing the lattice along the Cr-Cr bonds in [100] direction, 1D-chains are approached while compression along [-110] deforms the lattice towards a square lattice. Based on previous theoretical calculations, a transition to a non-frustrated Néel-type order is expected in an experimentally accessible strain range under [-110] compression. I will present stress-strain measurements which show a large first-order transition in the predicted strain range. The transition is accompanied with a stiffening of the lattice. XRD data taken under strain confirms large changes in the lattice parameters at this phase transition. However, recent neutron data revealed that this is an incommensurate-to-incommensurate phase transition rather than the expected incommensurate-to-Néel transition, which raises further questions.

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