Growth rate dependence of rare‐earth segregation in the liquid‐phase epitaxy of magnetic garnet films

摘要

Epitaxial films of the archetypical bubble garnet (R, Y)3Fe5O12, where R is a rare earth, were grown on (111) Gd3Ga5O12 substrates from a 200:1 by weight PbO:B2O3 flux using the horizontal dipping technique with rotation. Growth rate was varied by adjusting supercooling and rotation rate, and the equilibrium segregation coefficients of the dodecahedrally crystallizing cations KR = Rxtal/Rmelt were determined with reference to the film‐lattice constant and the segregation of these cations on octahedral sites. KR was found to obey the growth model of Burton, Prim, and Slichter [J. Chem. Phys. 21, 1987 (1953)], KR = KR0/[KR0+(1-KR0)e-kf], where f is the growth rate, KR0 is the segregation coefficient at zero growth rate, and k is a parameter which is a function of the thickness of the growth interface and the diffusion constant. The parameter k was found to be independent of the species R and to have the value 1.18 sec μm-1 for the particular growth condition. A strong correlation was found between KR0 and the partial molar heat of mixing of the R2O3 oxide and the flux, as calculated from regular solution theory [D. M. Gualtieri, J. Appl. Phys. 50, 2170 (1979)].