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Terada, Noriki*; Khalyavin, D. D.*; Manuel, P.*; Asai, Shinichiro*; Masuda, Takatsugu*; Saito, Hiraku*; Nakajima, Taro*; Osakabe, Toyotaka
Physical Review B, 110(2), p.024406_1 - 024406_9, 2024/07
The frustrated antiferromagnet CuFeO 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 (
3 GPa), as proved by the significant reduction in the critical magnetic field from 
=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 = 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.
studied by polarized and unpolarized neutron diffractionTerada, Noriki*; Qureshi, N.*; Stunault, A.*; Enderle, M.*; Ouladdiaf, B.*; Colin, C. V.*; Khalyavin, D. D.*; Manuel, P.*; Orlandi, F.*; Miyahara, Shin*; et al.
Physical Review B, 102(8), p.085131_1 - 085131_7, 2020/08
Times Cited Count：3 Percentile：18.79(Materials Science, Multidisciplinary)Terada, Noriki*; Khalyavin, D. D.*; Manuel, P.*; Osakabe, Toyotaka; Kikkawa, Akiko*; Kitazawa, Hideaki*
Physical Review B, 93(8), p.081104_1 - 081104_5, 2016/02
Times Cited Count：18 Percentile：62.53(Materials Science, Multidisciplinary)We performed neutron diffraction experiments under high pressures and high magnetic fields using a single crystal of the multiferroic compound TbMnO in order to clarify the mechanism associated with pressure/magnetic-field-induced giant ferroelectric polarization. We found that the E-type ordering of Mn spins induces giant ferroelectric polarization over all the parameter regions investigated, through an exchange striction mechanism. Furthermore, we propose that the polarization is reduced by polar ordering of the Tb moments in a zero magnetic field and is enhanced via the field-induced transition from polar to nonpolar Tb orderings at 2T.
Terada, Noriki*; Khalyavin, D. D.*; Manuel, P.*; Osakabe, Toyotaka; Radaelli, P. G.*; Kitazawa, Hideaki*
Physical Review B, 89(22), p.220403_1 - 220403_6, 2014/06
Times Cited Count：29 Percentile：74.35(Materials Science, Multidisciplinary)We have studied the pressure effect on the magnetic orderings in the strongly frustrated antiferromagnet CuFeO, by using neutron diffraction experiments under hydrostatic pressure. The main result is elucidation of the pressure-temperature magnetic phase diagram, consisting of the fourmagnetic phases including two polar ones. In particular, in the 3 GPa 
P 4 GPa pressure range, the ICM2 phase with the proper screw magnetic ordering stabilized. This polar phase is almost identical to the ferroelectric incommensurate (FEIC) phase induced by either a magnetic field or chemical doping. Furthermore, above 4 GPa, a new low-symmetry phase ICM3 is realized. This is unique for the family of delafossite multiferroics and implies an admixture of both cycloidal and proper screw spin configurations. The sequence of the observed magnetic phases with changing pressure might be attributed to pressure suppression of the monoclinic lattice distortions responsible for releasing the spin frustration in the system.
using hybrid anvil cellTerada, Noriki*; Osakabe, Toyotaka; Khalyavin, D. D.*; Manuel, P.*; Radaelli, P. G.*; Kitazawa, Hideaki*
no journal, ,
We have investigated the pressure effect on magnetic orderings in triangular lattice antiferromagnet CuFeO up to 3.2 GPa, by means of neutron diffraction experiments with the hybrid-anvil-cell. The magnetic ground state of CuFeO with 
= (1/4, 1/4, 3/2) in ambient pressure is changed in to the other magnetic state under pressure. In the pressure induced phase, we observed the magnetic reflections at (
, , 3/2) and (1-, 1-, 3/2), 
0.2 at 3.2 GPa and 1.5 K, which are the identical positions to those in field-induced or nonmagnetic impurity-induced noncollinear magnetic phase with ferroelectric polarization. This might suggest that pressure induces the ferro- electric phase in CuFeO.
