Demagnetization factor

Some common shapes have the following demagnetization factors (30). D = 0 for fields applied parallel to an infinite sheet... 

This critical field called coercivity ff. or switching field Ff., is also equal to FF. If a field is applied in between 0 and 90° the coercivity varies from maximum to zero. In the case of this special example the applied field Ha = Hs = Hc = Hk. Based on the classical theory, Stoner-Wohlfarth (33) considered the rotation unison for noninteracted, randomly oriented, elongated particles. The anisotropic axis can be due to the shape anisotropy (depending on the size and shape of the particle) or to the crystalline anisotropy. In the prolate ellipsoids b is the short axis and a the longest axis. The demagnetizing factors are IV (in the easy direction) and The demagnetizing fields can then be calculated by Hda = — Na Ms, and Hdb = — Nb Ms. The shape anisotropy field is Hd = (Na — Nb)Ms. Then the switching field Hs = Hd = (Na — Nb)Ms. 

The effect of the shape of a specimen on its magnetic behaviour, shape anisotropy , is expressed by a demagnetization factor Ad- A field Ha applied to a solid of arbitrary shape is reduced by a factor proportional to its magnetization M, so that the effective field Ht within the body is given by... 

For shape anisotropy, Kx = ju0(1-3D)Ms2/4, where D is the demagnetizing factor (D = 0 for long cylinders, D= 1/3 for spheres, and D = 1 for plates) [56]. It is important to note that shape anisotropy is limited to very small particles ( 2.2). In large particles, shape anisotropy is destroyed by internal flux closure, indicated at the bottom of Fig. 5(a). 

Here Ku is the switching layer uniaxial anisotropy and Ny, Nx the demagnetizing factors along the hard axis (small axis of ellipsoid) and easy axis direction( long axis of ellipsoid). 

The qualitative and quantitative analysis of obtained spectra has been carried out using the phenomenological equations for the resonance conditions of long cylinder. The influence of demagnetizing factors tends to the following equations for the longitudinal orientation of the magnetization it s eq. 2 and for the transversal it is ... 

Demagnetizing factor (dimensionless) N l/4ir Demagnetizing factor (dimensionless) N... 

The study of ferromagnetic substances sometimes introduces a complication that is not encountered with paramagnetic substances. This is the demagnetization factor produced by the presence of any ferromagnetic substance in a field. Depending on the size, shape, and specific magnetization of the sample, the initial field in which the sample may be placed suffers reduction up to 25 per cent or more. As ordinarily conducted, thermomagnetic studies of the type described above are not... 

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