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

被引：6

作者：

Holm-Dahlin, Sonja ^{[1
,2
]}

Janas, Sofie ^{[1
]}

Kreisel, Andreas ^{[3
]}

Pomjakushina, Ekaterina ^{[4
]}

White, Jonathan S. ^{[2
]}

Fennell, Amy L. ^{[4
]}

Lefmann, Kim ^{[1
]}

机构：

[1] Univ Copenhagen, Nanosci Ctr, Niels Bohr Inst, DK-2100 Copenhagen, Denmark

[2] Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland

[3] Univ Leipzig, Inst Theoret Phys, D-04103 Leipzig, Germany

[4] Paul Scherrer Inst, Lab Multiscale Mat Expt, CH-5232 Villigen, Switzerland

来源：

QUANTUM BEAM SCIENCE | 2018年 / 2卷 / 03期

关键词：

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

D O I：

10.3390/qubs2030016

中图分类号：

TH7 [仪器、仪表];

学科分类号：

0804 ; 080401 ; 081102 ;

摘要：

We investigated the antiferromagnetic phase transition in the frustrated and multiferroic hexagonal manganites h-YMnO3 (YMO) and h-(Y0.98Eu0.02)MnO3 (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 of TN=71.3(1) K and 72.11(5) K and the critical exponent 0.22(2) and beta=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 to TN=75.2(5) K, in agreement with earlier reports, while beta was 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, beta ', identical to the order parameter beta. Our results indicate that the gap in YEMO indeed closes at TN=72.4(3) K with beta '=0.24(2), while the in-pressure gap in YMO closes at 75.2(5) K with an exponent of beta '=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 for beta in the two systems support the likelihood of a new universality class for triangular, frustrated antiferromagnets.

引用

页数：19