The internal energies of Heisenberg magnetic systems

Abstract

The internal energies, including transverse and longitudinal parts, of quantum Heisenberg systems for arbitrary spin S are investigated by the double-time Green's function method. The expressions for ferromagnetic (FM) and antiferromagnetic (AFM) systems are derived when one component of magnetization is considered with the higher order longitudinal correlation functions being carefully treated. An unexpected result is that around the order and disorder transition points the neighboring spins in a FM (AFM) system are more likely longitudinally antiparallel (parallel) than parallel (antiparallel) to each other for S<=3/2 in spite of the FM (AFM) exchange between the spins. This is attributed to the strong quantum fluctuation of the systems with small S values. We also present the expressions of the internal energies of FM systems when the three-component of magnetizations are considered.

References in corpus (12)

• Many-body Green's function theory of Heisenberg films
• Many-body Green's function theory for the magnetic reorientation of thin ferromagnetic films
• Green's-function theory of the Heisenberg ferromagnet in a magnetic field
• Field-induced magnetic reorientation and effective anisotropy of a ferromagnetic monolayer within spin wave theory
• Thermodynamics of a two-dimensional frustrated spin-1/2 Heisenberg ferromagnet
• Thermodynamics of low dimensional spin-1/2 Heisenberg ferromagnets in an external magnetic field within Green function formalism
• Many-body Green's function theory for thin ferromagnetic anisotropic Heisenberg films: treatment of the exchange anisotropy
• Thermodynamics of the one-dimensional frustrated Heisenberg ferromagnet with arbitrary spin
• The Phase Transition of Square Lattice Antiferromagnets at Finite Temperature
• Thermodynamics of the frustrated one-dimensional spin-1/2 Heisenberg ferromagnet in a magnetic field
• The spectral theorem of many-body Green's function theory when there are zero eigenvalues of the matrix governing the equations of motion
• The treatment of zero eigenvalues of the matrix governing the equations of motion in many-body Green's function theory