Finite-size effects and compensation temperature of a ferrimagnetic small particle

Abstract

In this work we study the magnetic properties of a ferrimagnetic small particle on a hexagonal substrate. The particle is described by a mixed-spin Ising model in which the $\ensuremath{\sigma}=1∕2$ and $S=1$ spins are distributed in concentric and alternate hexagonal rings. We consider particles with different number of rings and show that particles with more than 11 shells can be considered as infinite systems. For a particle in which the finite-size effect is relevant, we investigated the role of the different parameters of the Hamiltonian in the appearance of a compensation temperature. As the model incorporates $\ensuremath{\sigma}\text{\ensuremath{-}}S,\ensuremath{\sigma}\text{\ensuremath{-}}\ensuremath{\sigma}$ and $S\text{\ensuremath{-}}S$ nearest-neighbor interactions, we observe the existence of a compensation point without the necessity of any next-nearest-neighbor interaction. The appearance of a compensation point depends only on the value of the $\ensuremath{\sigma}$ and $S$ intrasublattice couplings. The $\ensuremath{\sigma}$ intrasublattice interaction should be ferromagnetic and above a threshold value. On the other hand, the $S$ intrasublattice interaction should be mostly antiferromagnetic and restricted to a narrow range of values.