Abstract
MgCr2O4 is one of the best-known realizations of the pyrochlore-lattice Heisenberg antiferromagnet. The strong antiferromagnetic exchange interactions are perturbed by small further-neighbor exchanges such that this compound may in principle realize a spiral spin liquid (SSL) phase in the zero-temperature limit. However, a spin Jahn-Teller transition below TN≈13 K yields a complicated long-range magnetic order with multiple coexisting propagation vectors. We present neutron scattering and thermomagnetic measurements of MgCr2O4 samples under applied hydrostatic pressure up to P=1.7 GPa demonstrating the existence of multiple close-lying nearly degenerate magnetic ground states. We show that the application of hydrostatic pressure increases the ordering temperature by around 0.8 K per GPa and increases the bandwidth of the magnetic excitations by around 0.5 meV per GPa. We also evidence a strong tendency for the preferential occupation of a subset of magnetic domains under pressure. In particular, we show that the k=(0,0,1) magnetic phase, which is almost negligible at ambient pressure, dramatically increases in spectral weight under pressure. This modifies the spectrum of magnetic excitations, which we interpret unambiguously as spin waves from multiple magnetic domains. Moreover, we report that the application of pressure reveals a feature in the magnetic susceptibility above the magnetostructural transition. We interpret this as the onset of a short-range ordered phase associated with k=(0,0,1), previously not observed in magnetometry measurements.
Original language | English |
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Article number | 064415 |
Journal | Physical Review B |
Volume | 109 |
Issue number | 6 |
DOIs | |
State | Published - Feb 1 2024 |
Funding
We are grateful to Siân Dutton for her insights on interpreting our susceptibility data and to Collin Broholm for inspiration at the inception of this project. This project at GT (L.N., H.L., M.M.) was funded by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Award DE-SC-0018660. H. L. acknowledges additional financial support from the Royal Commission for the Exhibition of 1851. This research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The single-crystal synthesis work was supported as part of the Institute for Quantum Matter, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award DE-SC0019331. This work utilized the Materials Characterization Facility (MCF) jointly supported by Georgia Tech's Institute for Materials (IMat) and the Institute for Electronics and Nanotechnology (IEN), which is a member of the National Nanotechnology Coordinated Infrastructure supported by the National Science Foundation under Award ECCS-2025462. Data supporting this publication is available from Georgia Tech's Library at the following link: https://hdl.handle.net/1853/72958 .