Mixed Ising ferrimagnets with next-nearest neighbour
couplings on square lattices
Selke, W., Ekiz, C.
Institut für Theoretische Physik, Technische Hochschule Aachen, D-52056 Aachen, Germany; Adnan Menderes University, Aydin, Turkey
We study Ising ferrimagnets on square lattices with antiferromagnetic
exchange couplings between spins of values S=1/2 and S=1 on
neighbouring sites, couplings between S=1 spins
at next--nearest neighbour sites of the lattice, and a
single--site anisotropy term for the S=1 spins. Using
mainly ground state considerations and extensive
Monte Carlo simulations, we investigate various aspects of
the phase diagram, including compensation points, critical
properties, and temperature dependent anomalies. In contrast to previous
belief, the next--nearest neighbour couplings, when being of
antiferromagnetic type, may lead to compensation points.