Single ion anisotropy effects on a ferrimagnetic integer-spins system

Efectos de anisotropía de ion simple sobre un sistema ferrimagnético de espines enteros

The objective of this research is to analyze the thermomagnetic effects of an external magnetic field (h) and single ion anisotropies (D₁, D₂) on a ferrimagnetic system of alternating S = 1 and σ = 2 spins on a square lattice. The methodological analysis is done by means of phase diagrams of the magnetization, susceptibility and specific heat of the system, using computational simulations with Monte Carlo techniques and thermal bath type algorithms with periodic boundary conditions. Two ferrimagnetic models are considered: One with couplings between ions to first neighbors (S↔σ) and interactions of crystal (D₁, D₂) and external magnetic (h) fields, which describe the model J₁ - D₁ - D₂ - h (D₂ varies) and the second, with second-neighbor interactions for σ-type ions )  and crystal field interactions (D₁, D₂) through the model J₁ - J₃ - D₁ - D₂ (D₁ varies). Critical temperatures, first order phase transitions and compensation temperatures are found. We note a strong relationship between the critical temperature and the anisotropy fields. Finally, non-critical peaks are observed at low temperatures due to spin rearrangement in the sublattices, a direct consequence of the crystal fields given in the Hamiltonian.