Morphology transitions in three-dimensional domain growth with Gaussian random fields

Abstract

We study the morphology of magnetic domain growth in disordered three dimensional magnets. The disordered magnetic material is described within the random-field Ising model with a Gaussian distribution of local fields with width $\Delta$. Growth is driven by a uniform applied magnetic field, whose value is kept equal to the critical value $H_c(\Delta )$ for the onset of steady motion. Two growth regimes are clearly identified. For low $\Delta$ the growing domain is compact, with a self-affine external interface. For large $\Delta$ a self-similar percolation-like morphology is obtained. A multi-critical point at $({\Delta }_c$, $H_c({\Delta }_c))$ separates the two types of growth. We extract the critical exponents near ${\Delta }_c$ using finite-size scaling of different morphological attributes of the external domain interface. We conjecture that the critical disorder width also corresponds to a maximum in $H_c(\Delta )$.

8 pages, 10 figures, submitted to Phys. Rev. B

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• Depinning transition and thermal fluctuations in the random-field Ising model
• Influence of the temperature on the depinning transition of driven interfaces
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