Magnetoelectric Response in \(S=1/2\) Chain Helimagnets
One dimensional chain magnet with competing nearest and next nearest neighboring interactions (J1 and J2) is known as another textbook example of frustrated spin systems. In this chapter, we focus on the edge-shared CuO2 (or CuCl2) chain as an ideal stage to realize such a situation, and investigate their magnetoelectric response in detail. Notably, these compounds are characterized by S = 1/2 spin with strong quantum fluctuation, and the validity of the magnetoelectric coupling mechanisms proposed for classical spin systems are not trivial. By employing the polarized neutron scattering technique, we confirmed the coupling between spin vector chirality of cycloidal spiral structure and the direction of electric polarization on the quantum chain multiferroic LiCu2O2; This proves that the inverse Dzyaloshinskii-Moriya (D-M) mechanism still works even under the strong quantum fluctuation. We further investigated the magnetoelectric response of similar quantum chain magnets CuCl2, and confirmed that their dielectric behavior under rotating magnetic field can be also well reproduced within the framework of the inverse D-M scheme.
KeywordsElectric Polarization Quantum Fluctuation Magnetic Ground State Chain Magnet Spiral Spin
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