Pinning of domain walls

The mechanism for coercivity in the Cr—Co—Fe alloys appears to be pinning of domain walls. The magnetic domains extend through particles of both phases. The evidence from transmission electron microscopy studies and measurement of JT, and anisotropy vs T is that the walls are trapped locally by fluctuations in saturation magnetization. 

The origin of the nonlinearity and hysteresis in the films is most likely due to displacement of domain walls [4], If domain walls move in a medium with a random distribution of pinning center, the response of the material can be described, in the first approximation by Rayleigh relations. We next demostrate how optical interferometry can be sued to verify whether this particular model applies to the investigated pzt thin film. In the case of the converse piezoelectric effect, when the driving field E is varied between — Eo and Eo, the piezoelectric strain x is hysteretic and can be expressed by the following Rayleigh relations ... 

Sintered density (pore) pore becomes a pinning site of domain wall that prevents domain wall motion (Fig. 6.1.2). 

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