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We have used the effective field theory based on probability distribution method to investigate the hysteresis behavior of a magnetic nanoparticle with core/shell morphology in a random field. The hysteresis curves are obtained for different values of the random field and the temperature. We find a number of characteristic behaviors, such as the existence of double hysteresis loops for appropriate values of the system parameters. The remanent magnetization and the coercive field as a function of the temperature are examined.

Realizing room-temperature ferromagnetic interactions in diluted magnetic semiconductors is a precondition for the future application of next-generation spin-based information technologies. However, finding effective strategies to alter the inherent magnetic coupling remains difficult. This paper aims to propose an approach for manipulating the ferromagnetism of (0.12%, 0.18%, 0.25%) V-doped ZnO (V-ZnO). The influence of V doping on the structural, electronic, and magnetic properties of ZnO is studied using first principles pseudo-potential plane wave method within the density functional theory (DFT). According to the first-principles calculations, the ferromagnetic ground state is maintained by a half-metallic electronic structure resulting from substantial hybridization between V-3d and O-2p electrons, and the calculations suggest that the ferromagnetism could be governed by the interactions between cluster spines in the VO4 tetrahedra. With the magnetic coupling strengths obtained by the green's function method with the Wannier functions as a localized basis, the Monte Carlo simulation based on the Classical Ising model predicts the ferromagnetism of Zn 1 − x V x O (x = 0.12%, 0.18%, 0.25%) with T c = 55 K, 165 K and 345 K. The observed results show that, as a diluted magnetic semiconductor, V-doped ZnO is an excellent candidate. • Zn 1-x V x O with (x = 0.12, 0.18, and 0.25) exhibits a half-metallic ferromagnetic behavior. • Shifting of E f into the conduction band proves that V-doped ZnO is n-type semiconductor. • Monte Carlo simulation shows that V doped ZnO exhibits a T c above the room temperature. • Hysteresis loop become larger with the concentration of the V impurities. [ABSTRACT FROM AUTHOR]