Magnetisation processes and hysteresis

The increase in magnetic held leads to domain wall displacements until all the domains with orientations opposite to the held have been substituted by domains with directions parallel to H. However, there might be domains with orientation neither opposite nor parallel also, the applied held can have an orientation which does not coincide with an easy direction. In the general case, to attain the saturation state (in which the sample becomes a single domain oriented along the held direction). 

The domain wall displacement is not triggered by any field. There exists a threshold or critical field, H , below which the wall is not displaced. This critical field depends on sample defects walls are affected by any 

The critical held appears as a change of slope in the magnetisation 

A plot of permeability as a function of field is often useful to determine characteristics such as initial permeability, n and maximum permeability. Fig. 4.39. This plot represents the slope of the B(H) relationship, as a function of H. The initial part at low fields is the initial permeability, /ij, and the maximum corresponds therefore to u . Fig. 4.34. As H increases 

On the basis of this model, a quantitative description of magnetisation 

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