Continuous transformation between ferro and antiferro circular structures in frustrated Heisenberg model

Abstract

Frustrated magnetic compounds, in particular low-dimensional, are topical research due to the persistent uncovering of novel nontrivial quantum states and potential applications. The problem of this field is that many important results are scattered over the localized parameter ranges, while areas in between still contain hidden interesting effects. We consider the Heisenberg model on the square lattice and use the spherically symmetric self-consistent approach for spin–spin Green’s functions in ‘quasielastic’ approximation. We have found a new local order in spin liquids: antiferromagnetic isotropical helices. On the structure factor we see circular concentric dispersionless structures, while on any radial direction the excitation spectrum has ‘roton’ minima. That implies nontrivial magnetic excitations and consequences in magnetic susceptibility and thermodynamics. On the exchange parameters globe we discover a crossover between antiferromagnetic-like local order and ferromagnetic-like; we find stripe-like order in the middle. In fact, our ‘quasielastic’ approach allows investigation of the whole globe.