Sample size effect in coercivity measurement of epitaxial magnetic garnet films

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Abstract
The full set of characteristic parameters of epitaxial garnet films was measured as a function of the sample size from about 2000 to 5 mm2. The type of domain structure, width of the stripe domain period, characteristic material length, domain wall energy, and anisotropy did not change within the error of measurement on reducing the sample size. The bubble domain collapse field decreased by about 2.5%, and the domain wall coercivity was measured and found to have decreased—almost by an order of magnitude. The experiments showed the lack of dependence of coercivity on the domain wall length. The coercivity and collapse field are suggested as being related to the sample dimensions via the sample-size-dependent derivatives of the total free energy with respect to the domain wall positions. The assumption of the direct effect of the free energy derivatives on the coercivity is supported by a model experiment.

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