Propriedades magnéticas e termodinâmicas de um modelo triangular de spin heisenberg para a molécula Cu3(OH)

Abstract

Magnetism is one of the most important research fields in Statistical Physics and Condensed Matter Physics, which attracts the attention of many theoretical and experimental physicists. In order to understand the microscopic origins of magnetic properties, discover new phenomena and new materials for the development of a wide variety of technological applications, this work presents a study of low-dimensional spin systems (models that accurately describe a class of magnetic materials) to investigate the thermodynamic and magnetic properties of a triangular structure composed of spin-1/2 Heisenberg that addresses characteristics of the magnetic molecule Cu3(OH). The investigation took place through exact diagonalization and analysis of the energy spectrum and ground state phase diagrams. Subsequently, we determine the model’s partition function and, through it, define the thermodynamic and magnetic properties of the system, including magnetization, susceptibility, entropy, specific heat and magnetocaloric effect. The model presents ferromagnetic and ferrimagnetic phases, in addition to presenting degeneracy for some sets of parameters, due to this degeneracy the model presents residual entropy. The system has non-zero magnetization at T = 0 and two magnetization plateaus due to the configuration of the spins. We found double peaks in the specific heat curve indicating competition between energy levels. We identified the presence of isentropic curves in the null field and in the region close to the critical field, where the phase transition occurs.