Interplay of frustration and quantum fluctuations in a spin-1/2 anisotropic square lattice

Abstract

Motivated by theoretical and experimental studies reported by Yamaguchi et al. (Phys. Rev. B 98, 094402 (2018)), we performed a cluster mean-field analysis of an anisotropic Heisenberg model with six competing exchange interactions. We study the ground and thermal states by tuning the spin anisotropy, magnetic field, and temperature. Our results show that an external magnetic field induces quantum fluctuations, suppressing local moments and leading to the occurrence of a magnetization plateaulike state. When weak spin anisotropy is considered, the competing interactions are affected, and the field-induced fluctuations can lead to a well-defined magnetization plateau within a field range, in which an exotic quantum state can emerge. This state exhibits the coexistence of ferromagnetic and dimerized chains driven by the relation between frustration and the external field. Moreover, we identify a phase transition from a collinear antiferromagnetic order to a disordered state at a finite temperature. Our findings reveal unconventional magnetic properties at low temperatures that can guide future experimental studies of verdazyl-based compounds with anisotropic exchange interactions.