Surface-induced miscibility gap in vapor deposited Co{sub 1{minus}{ital x}}Pt{sub {ital x}} (abstract)
- Department of Physics, University of California at San Diego, La Jolla, California 92093-0139 (United States)
We have deposited (100) and (111) oriented single-crystal Co{sub 1{minus}{ital x}}Pt{sub {ital x}} films ({ital x}=0.65, 0.75, and 0.86) over a range of growth temperatures from {minus}50 to 800{degree}C. The Curie temperature is increased by up to 200{degree}C over the value expected for the homogeneous, chemically disordered alloy in the as-deposited films (of both orientations) grown near 400{degree}C. Measurements of the onset of magnetic ordering below the Curie temperature indicate separation into Co-rich and Pt-rich regions. High resolution x-ray measurements show no shift in the lattice constant or broadening of the x-ray peaks, and no observable strain for {ital x}=0.75, suggesting that the separated regions are small and epitaxially coherent. We interpret this as evidence for a previously unobserved miscibility gap. The bulk phase diagram shows no phase separation, but magnetic energy tends to drive the system toward immiscibility as demonstrated by the calculations of several workers. We suggest that the observed miscibility gap is an equilibrium {ital surface} effect, trapped into the bulk film by low bulk mobility. Preliminary work by Rosengren and Kundrotas supports this idea. Large perpendicular magnetic anistropy is found in those films that exhibit an anomalously high Curie temperature (films grown near 400{degree}C). This anisotropy is likely related to the phase separation. After annealing at high temperatures, the Curie temperature approaches the homogeneous values and the anisotropy relaxes. {copyright} {ital 1996 American Institute of Physics.}
- OSTI ID:
- 280074
- Report Number(s):
- CONF-951101-; ISSN 0021-8979; TRN: 9608M0131
- Journal Information:
- Journal of Applied Physics, Vol. 79, Issue 8; Conference: 40. conference on magnetism and magnetic materials, Philadelphia, PA (United States), 6-9 Nov 1995; Other Information: PBD: Apr 1996
- Country of Publication:
- United States
- Language:
- English
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