TY - JOUR

T1 - Anisotropyerature phase diagram for the two-dimensional dipolar Heisenberg model with and without magnetic field

AU - Komatsu, Hisato

AU - Nonomura, Yoshihiko

AU - Nishino, Masamichi

N1 - Funding Information:
The present study was supported by a Grant-in-Aid for Scientific Research C (No. 17K05508) from MEXT of Japan, and the Elements Strategy Initiative Center for Magnetic Materials (ESICMM) under the outsourcing project of MEXT. Some of the numerical calculations were performed on the Numerical Materials Simulator at the National Institute for Materials Science.
Publisher Copyright:
© 2019 American Physical Society.

PY - 2019/9/5

Y1 - 2019/9/5

N2 - We investigate phase transitions in the two-dimensional dipolar Heisenberg model with uniaxial anisotropy with a specific ratio between the exchange and dipolar constants, δ=1. We obtain the η-T (anisotropy vs temperature) phase diagrams for typical values of magnetic field by a Monte Carlo method with an O(N) algorithm. We find that at lower fields, the η-T phase diagram consists of the planar ferromagnetic (F), perpendicular stripe-ordered (SO), and paramagnetic (P) phases, and is characterized by the triple point. In the SO phase realized at larger η and smaller T, the SO pattern changes depending on the field. On the other hand, we find that at higher fields, the SO phase does not exist, while the planar F phase robustly remains. We study the properties of the phase boundaries in detail. We find that the slope of the spin-reorientation-transition line is positive with and without field, i.e., dηdT>0, which implies that the planar F phase changes to the SO phase with lowering temperature. In the phase diagrams we observe a characteristic shape of the P-planar F phase-transition line, whose maximum point of η is located at an intermediate temperature. This structure leads to the temperature-induced reentrant transition associated with P and planar F phases, which appears in successive phase transitions with lowering temperature: P → planar F → P → SO phase at lower fields and P → planar F → P phases at higher fields.

AB - We investigate phase transitions in the two-dimensional dipolar Heisenberg model with uniaxial anisotropy with a specific ratio between the exchange and dipolar constants, δ=1. We obtain the η-T (anisotropy vs temperature) phase diagrams for typical values of magnetic field by a Monte Carlo method with an O(N) algorithm. We find that at lower fields, the η-T phase diagram consists of the planar ferromagnetic (F), perpendicular stripe-ordered (SO), and paramagnetic (P) phases, and is characterized by the triple point. In the SO phase realized at larger η and smaller T, the SO pattern changes depending on the field. On the other hand, we find that at higher fields, the SO phase does not exist, while the planar F phase robustly remains. We study the properties of the phase boundaries in detail. We find that the slope of the spin-reorientation-transition line is positive with and without field, i.e., dηdT>0, which implies that the planar F phase changes to the SO phase with lowering temperature. In the phase diagrams we observe a characteristic shape of the P-planar F phase-transition line, whose maximum point of η is located at an intermediate temperature. This structure leads to the temperature-induced reentrant transition associated with P and planar F phases, which appears in successive phase transitions with lowering temperature: P → planar F → P → SO phase at lower fields and P → planar F → P phases at higher fields.

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U2 - 10.1103/PhysRevB.100.094407

DO - 10.1103/PhysRevB.100.094407

M3 - Article

AN - SCOPUS:85072559673

SN - 2469-9950

VL - 100

JO - Physical Review B

JF - Physical Review B

IS - 9

M1 - 094407

ER -