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Theory of domain wall motion induced by microwave magnetic fields

1975; IEEE Magnetics Society; Volume: 11; Issue: 4 Linguagem: Inglês

10.1109/tmag.1975.1058785

1941-0069

Ernst Schlömann,

Magneto-Optical Properties and Applications

A general theory is developed that applies to arbitrary polarization and takes account of damping and of the dipolar interaction between domains. The effect of the microwave field on the domain structure can be characterized by a pressure on the domain walls and by an alignment energy, both of which are proportional to the square of the rf magnetic field and become large in the vicinity of a resonance. For circular polarization the pressure tends to decrease the Larmor-domains (domains in which the imposed sense of polarization coincides with the sense of the natural spin precession) for frequencies outside the resonance region. Inside the resonance region, however, the pressure tends to increase the Larmor-domains. A linearly polarized field also exerts a pressure on the domain walls, with the polarity dependent upon the orientation of the field to the wall normal. In a linearly polarized magnetic field the domain walls tend to become aligned parallel to the rf field at frequencies ω near the low-frequency resonance (ω =γH a , γ = gyromagnetic ratio, H a = anisotropy field) and perpendicular to the rf field at frequencies near the high-frequency resonance (ω = γ[H a (H a + 4πM 0 )] 1/2 , M 0 = saturation magnetization).