Exploring new members of magnetoelectric materials in CuO–CuCl2–SeO2 system

Materials containing Cu2+ ions with quantum spin S = 1/2 and oxyhalide groups are an intriguing avenue for exploring quantum-magnetic phenomena. The CuO–CuCl2–SeO2 system has captured significant attention within the research community because of its potential to unveil new magnetic phases and their corresponding properties. Over the past decade, numerous researchers have investigated the unique physical properties of various compounds in this system and their structural correlations. In this study, we investigate the structural, magnetic, and magnetoelectric properties of three compounds: Cu3(SeO3)2Cl2, Cu5(SeO3)4Cl2, and Cu7O2(SeO3)2Cl6. The detailed magnetic and dielectric properties of Cu3(SeO3)2Cl2 indicate antiferromagnetic ordering at TN = 38 K with a dielectric anomaly independent of the magnetic origin, whereas Cu5(SeO3)4Cl2 shows finite magnetoelectric coupling near TN = 42 K. More importantly, we successfully synthesized the Nicksobolevite Cu7O2(SeO3)2Cl6 compound, which is a more complex structure, from the CuO–CuCl2–SeO2 system. Interestingly, Cu7O2(SeO3)2Cl6 and Cu2+ ions formed a spin-frustrated lattice with a cluster of corners sharing Cu2+ tetrahedra connected by eight Cu atoms running along the crystallographic b-axis. Complex magnetism with canted antiferromagnetic ordering at TN = 11 K was consistent with the finite hysteresis in the M-H curve, specific heat Cp, and dielectric anomaly, indicative of strong magnetoelectric coupling. Additionally, systematic changes in the magneto-dielectric behavior after magnetoelectric poling revealed resilient coupling between the magnetic and electric domains. Our study provides insights into the unique properties of these compounds and offers a detailed comparison with other multiferroic compounds in the CuO–CuCl2–SeO2 system. [Display omitted] •We provide a concise review of the crystal structure and physical properties of key compounds from the CuO–SeO2–CuCl2 ternary phase diagram, including CuO, CuCl2, Cu2OCl2, Cu2OSeO3, Cu5O2(SeO3)2Cl2, and Cu9O2(SeO3)4Cl6.•Dielectric and magnetic analyses of Cu3(SeO3)2Cl2 and Cu5(SeO3)4Cl2 suggest the presence of finite magnetoelectric coupling below TN.•For the first time we have successfully synthesized Cu7O2(SeO3)2Cl6 compound, our experimental findings reveal that among all the compounds within the CuO–SeO2–CuCl2 ternary phase diagram, Cu7O2(SeO3)2Cl6 exhibits a more complex crystal structure with eight distinct Cu2+ atoms and demonstrates intriguing magnet