Analytic Research On Magnetic And Thermodynamic Properties Of Magnetic Thin Film

Magnetic thin film will be widely applied to magnetic recording medium of super high density, magneto-optic recording medium, thin film magnetic head and sensor. At present, some progresses have been made in the research on the theory and practice of magnetic thin film magnetic properties and thermodynamic properties, but there are some gaps far from the exploitation and application of magnetic thin film. Around the research to the theory and practice of magnetic thin film magnetic properties and thermodynamic properties in this paper, in the s-d commutative operation and Heisenberg model and by variational cumulant expansion and spin Green Function method, the magnetic and thermodynamic properties have been studied for system of Heisenberg magnetic thin film and ferromagnetic granule film with ferromagnetic granule, such as the spin excitated relaxation, spin excitation spectrum and spin polarization excitation spectrum, spontaneous magnetization, effective damping coefficient, energy dissipation and critical behavior etc., as a result, the laws have been achieved for its changing with layers of the film, the size of granule and temperature, so the results are well conformed to the experiments.The results show: 1)For the quantum Heisenberg film, the spontaneous magnetization depends on the number of atomic layers and decreases rapidly as the number of atomic layers is decreased The internal energy and specific heat is in relation to temperature, not continuous in the critical reduced temperature and changing very greatly. 2)The spin excitated relaxation of ferromagnetic granule film with ferromagnetic granule will change with temperature, the size of granule, excitated mode, and the process of the spin excitation relaxation through spin-polarized excitation is not related to temperature, however, the one through thermal excitation is.3)The frequency of the spin-wave excitation spectrum is higher, while the size of granule smaller. The frequency is not related to temperature, and spin-polarized excitation spectrum is, and it shows different properties from those of ferromagnetic massive crystal spin wave spectrum.4)With the outfield bi-layer film spin wave sympathetic vibration, 2ΔH , the breadth of spin wave spectrum is related with wave vector, thickness, damping parameter and spin susceptibility and the spin wave vector in the excitation layer. In the bi-layer films with large differences, 2ΔH , the breadth of spin wave spectrum is enlarged with the spin wave vector in the excitation layer. The systematical researches on the theory of magnetic thin film magnetic and thermodynamic properties will be the powerful theoretical evidence for the experiments and developments of magnetic thin film in this paper, and the results will be theoretical and practical to enrich and improve the theory and development of magnetic thin film research. Thus, an active train of thought has been achieved for the further researches in this field.