Electric, Dielectric, and Phonon Properties of Cu₂OCl₂

Investigating the multiferroic properties of , their temperature and magnetic‐field dependencies around the magnetic and ferroelectric phase transition temperatures and are analyzed using a microscopic model and Green's function technique. Near the Neel temperature , a kink in the specific heat and also in the phonon energy and damping due to strong anharmonic spin–phonon interaction is observed. The kink in disappears with increasing magnetic field h . The polarization shows also a small anomaly at and decreases with increasing magnetic field h . This behavior strongly suggests that exhibits multiferroic characteristics. A kink at can be seen in the real part of the dielectric constant , too. It should be noted that demonstrates a significant increase with increasing field strength h below , which is a pronounced magneto‐dielectric effect. These findings qualitatively agree with the experimental data.