Magnetic susceptibility of a ternary Ising nanoisland

Abstract

We investigate magnetic properties of a ternary ( 1 / 2 , 1, 3 / 2 ) bilayer Ising nanoisland with an 18-site quadratic structure. By employing exact enumeration, we study the effects of crystal fields, exchange couplings and thermal fluctuations on the magnetic susceptibility and blocking temperature. As a result, we find several scenarios in which a double peak structure in the thermal dependence of the magnetic susceptibility can be observed. In particular, the competition between core–shell antiferromagnetic interactions and the external magnetic field can drive an additional low-temperature maximum in the magnetic susceptibility. In addition, the competition between core–shell couplings and a strong crystal field in the core spins can also provide a scenario in which the magnetic susceptibility shows two maximum. From the magnetic susceptibility maximum at higher temperatures, we estimate the blocking temperature. Surprisingly, we note that an increase in the absolute value of the exchange couplings can reduce the blocking temperature. Moreover, our findings suggest that the mechanism driving the double maxima in the magnetic susceptibility also provides a context in which the increase in the strength of the exchange coupling can lead to a reduction in the blocking temperature. Therefore, our results allow us to describe different scenarios in which double-peak structures in the magnetic susceptibility of nanoparticles can be spotted, also suggesting that these scenarios can favor a reduced blocking temperature. • Magnetism of a mixed-spin (1/2,1,3/2) nanoisland with core–shell structure has been investigated. • Effects of crystal fields and exchange couplings are evaluated. • Thermal dependence of magnetic susceptibility shows a double-peak structure. • Blocking temperature shows non-monotonic dependence on the core–shell couplings.