Study Of The Dispersion Relation And Delay Of The Magnetic Nano-granular Films

With the development of electrical instruments to small-sized and high performance, the research about multifunction and high frequency of these instruments has become a living field. The instruments should better have a high magnetic conductivity, a high saturated magnetic induction and a moderate anisotropic field. The magnetic nano-granular films with iron or cobalt elements have a high electrical resistivity, a high intensity of saturated magnetic induction and a wide frequency of magnetic conductivity, thus it is a realistic material to make micro-magnetic instruments.In this paper, I have made a deep-going research about dispersion relation, thermodynamic properties and delay by Green-function method, that is: (1) Taking the Fe-SiO₂ disorder granular film as a case, we have got its spin wave excitation and spin-polarization excitation dispersion relation, the variation law with temperature and granular diameter, even the variation law of magnetization, the magnetic conductivity and heat capacity with temperature. (2) On the basis of the spin wave excitation damp coefficient, and taking the (α -C: H)_1-xCo_x disorder granular film as a case, we have got the variation law of spin wave excitation delay with temperature. Moreover, by Bolthzman statistic method, we have derived the average magnetization of thin-cylinder periodical granular films, the phase transition condition, the variation law of the granular average magnetization of ferromagnetic order to anti-ferromagnetic order with temperature.The above research I did is useful in a certain way for the understanding of the magnetism, thermodynamics and energy loss of the nano-ferromagnetic granular films.