Ferromagnetism out of charge fluctuation of strongly correlated electrons in κ-(BEDT-TTF)2Hg(SCN)2Br

• Published in: npj quantum materials 2021-10, Vol.6 (1), p.1-8, Article 87
• Main Authors: Yamashita, Minoru, Sugiura, Shiori, Ueda, Akira, Dekura, Shun, Terashima, Taichi, Uji, Shinya, Sunairi, Yoshiya, Mori, Hatsumi, Zhilyaeva, Elena I., Torunova, Svetlana A., Lyubovskaya, Rimma N., Drichko, Natalia, Hotta, Chisa
• Format: Article
• Language: English
• Subjects: 639/766/119/2793; 639/766/119/997; Antiferromagnetism; Condensed Matter Physics; Curie temperature; Dimers; Dipoles; Domains; Ferromagnetism; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Insulators; Low temperature; magnetic materials; Magnetic permeability; magnetic properties; Magnetism; MATERIALS SCIENCE; Phase transitions; Physics; Physics and Astronomy; Quantum Physics; Structural Materials; Surfaces and Interfaces; Thin Films; Transition temperature
• ISSN: 2397-4648; 2397-4648
• DOI: 10.1038/s41535-021-00387-6

We perform magnetic susceptibility and magnetic torque measurements on the organic κ -(BEDT-TTF) 2 Hg(SCN) 2 Br, which is recently suggested to host an exotic quantum dipole-liquid in its low-temperature insulating phase. Below the metal-insulator (MI) transition temperature, the magnetic susceptibility follows a Curie–Weiss law with a positive Curie–Weiss temperature, and a particular M ∝ H curve is observed. The emergent ferromagnetically interacting spins amount to about 1/6 of the full spin moment of localized charges. Taking account of the possible inhomogeneous quasi-charge-order that forms a dipole-liquid, we construct a model of antiferromagnetically interacting spin chains in two adjacent charge-ordered domains, which are coupled via fluctuating charges on a Mott-dimer at the boundary. We find that the charge fluctuations can draw a weak ferromagnetic moment out of the spin singlet domains.