The Magnetic Phase Transition and Universality Class of h-YMnO3 and h-(Y0.98Eu0.02)MnO3 Under Zero and Applied Pressure

Quantum Beam Science

White, Jonathan S.¹  Kreisel, Andreas²  Pomjakushina, Ekaterina³  Janas, Sofie⁴  Holm-Dahlin, Sonja⁵ 

[1] Author to whom correspondence should be addressed;Institut für Theoretische Physik, Universität Leipzig, 04103 Leipzig, Germany;Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland;Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland;Nanoscience Center, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark

关键词: critical exponent;    multiferroics;    spin-wave;    magnetic phase transition;    applied pressure;    inelastic neutron scattering;   

DOI  :  10.3390/qubs2030016

学科分类：电子、光学、磁材料

来源: mdpi

【 摘 要 】

We investigated the antiferromagnetic phase transition in the frustrated and multiferroic hexagonal manganites h-YMnO 3 (YMO) and h-(Y0.98 Eu0.02 )MnO 3 (YEMO). Elastic neutron scattering was used to study, in detail, the phase transition in YMO and YEMO under zero pressure and in YMO under a hydrostatic pressure of 1.5 GPa. Under conditions of zero pressure, we found critical temperatures ofT N= 71.3( 1 )K and 72.11 ( 5 ) K and the critical exponent 0.22 ( 2 ) and β = 0.206 ( 3 ), for YMO and YEMO, respectively. This is in agreement with earlier work by Roessli et al. Under an applied hydrostatic pressure of 1.5 GPa, the ordering temperature increased toT N= 75.2( 5 )K, in agreement with earlier reports, whileβwas unchanged. Inelastic neutron scattering was used to determine the size of the anisotropy spin wave gap close to the phase transition. From spin wave theory, the gap is expected to close with a critical exponent, β ′, identical to the order parameterβ . Our results indicate that the gap in YEMO indeed closes atT N= 72.4( 3 )K withβ ′= 0.24( 2 ) , while the in-pressure gap in YMO closes at 75.2(5) K with an exponent ofβ ′= 0.19( 3 ) . In addition, the low temperature anisotropy gap was found to have a slightly higher absolute value under pressure. The consistent values obtained forβin the two systems support the likelihood of a new universality class for triangular, frustrated antiferromagnets.

【 授权许可】

CC BY