Magnetic properties of XXZ Heisenberg antiferromagnetic and ferromagnetic core-shell nanowires

Abstract

A cylindrical core-shell nanowire was described by an anisotropic XXZ Heisenberg model. The spontaneous magnetization, critical temperature, and hysteresis behavior were calculated by using the double-time spin Green's function method. For the nanowire with antiferromagnetic interfacial exchange interaction, the spin quantum fluctuation of the core is more obvious than that of the shell. The critical temperature of the system does not change for the same values of the antiferromagnetic or ferromagnetic interfacial exchange interaction, and it reduces to zero when the exchange anisotropy parameter reaches 1.0. The asymptotic value of the ratio of magnetizations from the shell to the core as the temperature approaches the critical temperature shows interesting behaviors during the interaction between spins in the core or the shell changing from Ising limit to Heisenberg limit. The magnetic hysteresis of the system with antiferromagnetic interfacial exchange interaction shows behaviors of magnetization plateaus, single loop, double loops, and tricyclic loops. When the interfacial exchange interaction is ferromagnetic, the hysteresis only shows single loops.