NMR evidence of charge fluctuations in multiferroic CuBr<sub>2</sub>

NMR evidence of charge fluctuations in multiferroic CuBr₂

Wang Rui-Qi^{1, 2}, Zheng Jia-Cheng², Chen Tao², Wang Peng-Shuai², Zhang Jin-Shan³, Cui Yi², Wang Chao⁴, Li Yuan⁴, Xu Sheng^{1, †}, Yuan Feng^{1, ‡}, Yu Wei-Qiang²

(color online) (a) Magnetic susceptibility χ ( T ) of CuBr₂ as a function of temperature, with a 1000 Oe magnetic field applied in the ab-plane, under zero-field-cooling (ZFC) condition. Inset: the temperature derivative, d χ / d T . The blue arrow points at a sharp peak characterizing the magnetic transition at T^N. (b) The ac dielectric constant ε of the sample measured under different magnetic fields, with capacitance measurement frequency of 20 kHz. The magnetic field are applied along the ab-plane of the crystal. Inset: The enlarged view of the data close to transition temperature T_N.