Elastic and inelastic neutron scattering experiments under high pressure in the frustrated antiferromagnet CuFeO2

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The frustrated antiferromagnet CuFeO₂ exhibits pressure-induced complex magnetic phase transitions from the commensurate collinear (CM1) phase to several incommensurate noncollinear phases. To study the effect of high pressure on magnetic interactions, we performed neutron diffraction and inelastic neutron scattering experiments under high-pressure conditions. With increasing pressure, the CM1 ground state becomes less stable against application of a magnetic field even below the critical pressure (P≤3 GPa), as proved by the significant reduction in the critical magnetic field from Hc1=7.5 T to 4.5 T at 2.1 GPa. Additionally, the energy gap in the spin-wave dispersion relation is reduced from 1.0 to 0.88 meV by the application of a pressure of $P=2.1$ GPa. Comparing the experimental results with spin-wave calculations revealed that the change in the spin-wave excitation can be explained by the reduction in either the uniaxial anisotropy term or the degree of separation in the nearest-neighbor exchange interactions.