2023/11/28 by Sebin J. Sebastian, Sebastian, Sebin J., S. Mohanty +11 · 1 voice
Physics and Astronomy · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Strongly Correlated Electrons (cond-mat.str-el) #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.48550/arxiv.2311.16890
We present the magnetic properties of a strongly spin-orbit coupled quantum dimer magnet based on Co2+. The metal-organic framework compound Co2(BDC)2(DPTTZ)2⋅DMF features Co2+ dimers arranged nearly orthogonal to each other, similar to the Shastry-Sutherland lattice. Our assessment based on the magnetization and heat capacity experiments reveals that the magnetic properties at low temperatures can be described by an effective J\rm eff = 1/2 Kramers doublet and the ground state is a singlet with a tiny spin gap. Although the magnetic susceptibility could be analyzed in terms of the interacting dimer model with an isotropic intradimer coupling J0/k\rm B ≃ 7.6 K, this model fails to reproduce the shape of magnetization isotherm and heat capacity data. A model of isolated spin dimers with the anisotropic exchange couplings Jxy ≃ 3.5 K and Jz ≃ 11 K provides an adequate description to the magnetic susceptibility, magnetization isotherm, and heat capacity data at low temperatures. Interestingly, no field-induced quantum phase phase is detected down to 100~mK around the critical field of gap closing, suggesting the absence of Bose-Einstein condensation of triplons and establishing isolated dimers with a negligible interdimer coupling.