Magnetoelectric Behavior from S=1/2 Asymmetric Square Cupolas.
Magnetoelectric properties are studied by a combined experimental and theoretical study of a quasi-two-dimensional material composed of square cupolas, Ba(TiO)Cu_{4}(PO_{4})_{4}. The magnetization is measured up to the field above the saturation, and several anomalies are observed depending on the field directions. We propose a S=1/2 spin model with Dzyaloshinskii-Moriya interactions, which reproduces the full magnetization curves well. Elaborating the phase diagram of the model, we show that the anomalies are explained by magnetoelectric phase transitions. Our theory also accounts for the scaling of the dielectric anomaly observed in the experiments. The results elucidate the crucial role of the in-plane component of Dzyaloshinskii-Moriya interactions, which is induced by the noncoplanar buckling of a square cupola. We also predict a "hidden" phase and another magnetoelectric response, both of which appear in a nonzero magnetic field.
Department of Applied Physics, The University of Tokyo, Hongo, 7-3-1, Bunkyo, Tokyo 113-8656, Japan.
Yasuyuki
Y
Kato
Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Kenta
K
Kimura
Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Atsushi
A
Miyake
Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Masashi
M
Tokunaga
Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Akira
A
Matsuo
Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Koichi
K
Kindo
Center for Advanced High Magnetic Field Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Mitsuru
M
Akaki
Center for Advanced High Magnetic Field Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Masayuki
M
Hagiwara
Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Masakazu
M
Sera
Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Tsuyoshi
T
Kimura
Department of Applied Physics, The University of Tokyo, Hongo, 7-3-1, Bunkyo, Tokyo 113-8656, Japan.
Yukitoshi
Y
Motome