Effect of growth atmosphere on rare-earth iron garnets grown from PbO based fluxes.

The growth atmosphere over a PbO fluxed melt can significantly affect the platinum and lead concentrations and the magnetic properties of rare-earth iron garnet films grown from that melt. We have investigated this effect using the simple composition (Gd2.5Eu0.5)Fe5O12. The films were grown in N2, air, and O2 atmospheres on (111) MgCaZr substituted GGG substrate (substrate lattice parameter a(o)=12.497angstroms) by conventional LPE techniques from PbO and PbO/B2O3 fluxes. Lead is incorporated self- compensatingly from the flux as Pb(2+) and Pb(4+). The oxygen partial pressure of the growth atmosphere affects the platinum incorporation in the film through the equilibrium between neutral elemental Pt(o) and ionic Pt(4+) species in the melt. Incorporation of elemental species such as Pt(o) in the film is unfavorable, but oxidized Pt(4+) ions are accommodated in the lattice in concentrations that depend on their melt concentrations and distribution coefficients.