Schwinger boson theory of anisotropic ferromagnetic ultrathin films

Article

关键词: SPIN-REORIENTATION TRANSITIONS;    TEMPERATURE-DEPENDENCE;    THIN-FILMS;    MAGNETIC-ANISOTROPY;    MAGNETOCRYSTALLINE ANISOTROPY;    UNIAXIAL FERROMAGNETS;    QUANTUM FERROMAGNETS;    HEISENBERG MODELS;    PHASE-TRANSITION;    1/N EXPANSION;   

DOI  :  10.1103/PhysRevB.62.5634

来源: SCIE

【 摘 要 】

Ferromagnetic thin films with magnetic single-ion anisotropies an studied within the framework of Schwinger bosonization of a quantum Heisenberg model. Two alternative bosonizations are discussed. We show that qualitatively correct results are obtained even at the mean-field level of the theory, similar to Schwinger boson results for other magnetic systems. In particular, the Mermin-Wagner theorem is satisfied: a spontaneous magnetization at finite temperatures is not found if the ground state of the anisotropic system exhibits a continuous degeneracy. We calculate the magnetization and effective anisotropies as functions of exchange interaction, magnetic anisotropies, external magnetic field, and temperature for arbitrary values of the spin quantum number. Magnetic reorientation transitions and effective anisotropies are discussed. The results obtained by Schwinger boson mean-field theory are compared with the many-body Green's-function technique.

【 授权许可】

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