Magnetoelectric Behavior from $S=1/2$ Asymmetric Square Cupolas

Abstract

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 above the saturation field, and several anomalies are observed depending on the field directions. We propose a $S$=1/2 spin model with Dzyaloshinskii-Moriya interactions, which well reproduces the full magnetization curves. 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 experiments. The results elucidate the crucial role of the in-plane component of Dzyaloshinskii-Moriya interactions, which is induced by the noncoplanar buckling of square cupola. We also predict a `hidden' phase and another magnetoelectric response both of which appear in nonzero magnetic field.

5 pages, 5 figures

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• Dual nature of improper ferroelectricity in a magnetoelectric multiferroic
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Cited by in corpus (5)

• Manipulating magnetoelectric effect -- Essence learned from Co${}_4$Nb${}_2$O${}_9$
• Spin-orbital-momentum locking under odd-parity magnetic quadrupole ordering
• Magnetic structure of Ba(TiO)Cu${}_4$(PO${}_4$)${}_4$ probed using spherical neutron polarimetry
• Magnetoelectric spectroscopy of spin excitations in LiCoPO4
• Optical Hall response in spin-orbit coupled metals: Comparative study of magnetic cluster monopole, quadrupole, and toroidal orders