Growth-induced anisotropy in bubble garnet films containing calcium
Conference
·
· AIP (Am. Inst. Phys.) Conf. Proc.; (United States)
OSTI ID:7125085
The growth-induced anisotropy, K/sub u/ measured on (111) LPE films of Eu/sub 3-x/Ca/sub x/Si/sub x/Fe/sub 5-x/O/sub 12/ grown on Sm/sub 3/Ga/sub 5/O/sub 12/ substrates is large and positive (K/sub u/ = 4.0 to 8.1 x 10/sup 4/ ergs/cm/sup 3/ for x = 0.5). Many experiments have shown that K/sub u/ in Eu/sub 3-x/Y/sub x/Fe/sub 5-y/Ga/sub y/O/sub 12/ films is also positive. In films of compositions (YSmCa)/sub 3/(GeFe)/sub 5/O/sub 12/, the effects of Ca and of Y on the growth-induced anisotropy are the same in sign and similar in magnitude. Since Ca/sup 2 +/ is larger in ionic radius than Eu/sup 3 +/ or Sm/sup 3 +/, whereas Y/sup 3 +/ is smaller, the simple site selectivity model of growth-induced anisotropy would predict opposite signs of K/sub u/ for the Ca and Y additions. This contradiction shows that ionic radius is not the only relevant parameter which determines growth-induced anisotropy in garnets, although size differences have been shown to account for the observed effects within the rare earth series. The charge difference between the Ca/sup 2 +/ ions and the rare earth ions, or the pairing of Ca/sup 2 +/ and Ge/sup 4 +/ or Si/sup 4 +/ ions during crystal growth may influence the site preference of the Ca ions and the resulting anisotropy. The growth-induced anisotropy of the Eu/sub 2/./sub 5/Ca/sub 0/./sub 5/Si/sub 0/./sub 5/Fe/sub 4/./sub 5/O/sub 12/ film, grown at 835/sup 0/C at a rate of 2 ..mu..m/min, annealed out after several hours at 900/sup 0/C in oxygen. This temperature is much lower than the usual annealing temperatures of 1200 to 1300/sup 0/C in O/sub 2/ which are required to reduce K/sub u/ in other bubble garnets. This is attributed to a high concentration of defects due to an imbalance in the Ca-Si concentrations in films grown at low temperatures and large growth rates.
- Research Organization:
- Bell Labs., Murray Hill, NJ
- OSTI ID:
- 7125085
- Conference Information:
- Journal Name: AIP (Am. Inst. Phys.) Conf. Proc.; (United States) Journal Volume: 34
- Country of Publication:
- United States
- Language:
- English
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