| In the information age, data storage is an important part of information processing, and magnetic recording storage is the most important way of data storage.According to statistics,92%of the new information is stored by magnetic recording.Past two decades, as in magnetic random access memory and ultra-high density storage technology applications, ferromagnetic films, ultra-thin films, intrinsical magnetic property and so on is one of the key and difficult points of the study.Meiklejohn and Bean discovered exchange bias in ferromagnetic/antiferromagnetic hybrid system in1956, and Diney found enhanced magnetoresistance spin valve in the design of ferromagnetic/antiferromagnetic bilayers in1991. Ferromagnetic/antiferromagnetic bilayers are widely used in magnetic sensors, magnetic recording read head and the random access memory and non-contact magnetron components.The physical properties of ferromagnetic/antiferromagnetic double layer films is very important, and has become one of the focus in today’s condensed matter physics.The most basic measurement method of exchange bias is the hysteresis loop method, exchange magnetization method,and ferromagnetic resonance,and ferromagnetic resonance method can measure the magnetic anisotropy and magnetic relaxation.With the development of computer and network technology, people need higher and higher data storage density. But the increased density of the magnetic recording faces enormous challenges,and the most important challenge is to overcome the superparamagnetic phenomenon.lt is encouraging that the perpendicular magnetic recording can solve this problem.Therefore, the perpendicular magnetic recording media is to achieve the key of high density vertical magnetic storage.Because magnetic membrane exist significance in physics research and practical application, this article chose "ferromagnetic resonance phenomenon of Magnetic membrane system" as a research subject.We use the free energy of variational method,and we focus on anisotropic of the magnetic membrane system, exchange of bias,ferromagnetic resonance phenomenon.This paper studies the following two questions: 1-. In Ferromagnetic/antiferromagnetic bilayers,measurement of exchange bias and magnetic anisotropy by ferromagnetic resonanceThe effective magnetic field caused by exchange coupling between a ferromagnetic and an antiferromagnetic bilayer and magnetic anisotropy has been investigated by means of ferromagnetic resonance. It shows that the exchange bias phenomenon occurrence and its positive or negative characteristic for ferromagnetic/antiferromagnetic bilayer can be identified from its magnetic resonance technique. In addition, when the field applied along different crystalline directions, the behavior of magnetic resonance field will be changed but closely depend on magnetocrystalline anisotropy and unidirectional anisotropy induced by the interface coupling in ferromagnetic/antiferromagnetic bilayer. Anomalies in the ferromagnetic resonance frequency studied as a function of applied field including its orientation and strength are interpreted as evidence for the four fold anisotropy, unidirectional anisotropy. Our conclusions are in good agreement with the related experiments.2^In ferromagnetic single-layer film, Magnetic thin film ferromagnetic resonance phenomenon in the vertical FieldWith the ferromagnetic resonance frequency as a function of the external magnetic field, ferromagnetic resonance phenomenon is investigated in the vertical field. The results show that for systems with external magnetic field parallel to the surface and perpendicular to the uniaxial magnetic anisotropy, magnetic resonance frequency is divided into two categories of low frequency branch and high frequency branch, their specific dependency relations depends on the magnetic film magnetic anisotropy; As to external magnetic field perpendicular to the system surface, the magnetic resonance frequency exists only a branch with the change of external magnetic field. In general, magnetic resonance frequency is nonlinear monotone decreasing with the increase of the external magnetic field. However, when the cubic magnetocrystalline anisotropy fieldHk] and uniaxial magnetocrystalline anisotropy field Ha ratio is2/3<|Hk1/Ha|<1, magnetic resonance frequency increases with the increase of the external magnetic field. So we can differentiate vertical magnetic anisotropy in magnetic thin films. |
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