Correlations between morphology, crystal structure and magnetization of epitaxial cobalt-platinum films grown with pulsed laser ablation
J. Appl. Phys. 103, 023915 (2008) The effects of growth rate (G_r), deposition temperature (T_d), film thickness (t_F), and substrate induced strain (epsilon) on morphological, crystallographic and magnetic characteristics of equiatomic CoPt epitaxial films synthesized with PLD are investigated. The...
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| Main Authors: | , , , , , , |
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| Format: | Journal Article |
| Language: | English |
| Published: |
04-03-2008
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | J. Appl. Phys. 103, 023915 (2008) The effects of growth rate (G_r), deposition temperature (T_d), film
thickness (t_F), and substrate induced strain (epsilon) on morphological,
crystallographic and magnetic characteristics of equiatomic CoPt epitaxial
films synthesized with PLD are investigated. The (001) substrates of MgO, STO
and LAO provide different degree of epitaxial strain for growth of the
disordered face centered cubic (fcc) and ordered face centered tetragonal
(L1_0) phases of CoPt. The films deposited at T_d~600 ^0C on all three
substrates are fcc with in-plane magnetization and a narrow hysteresis loop of
width~200 Oe. The L1_0 phase, stabilized only at T_d~700 ^0C becomes
predominantly c-axis oriented as T_d is increased to 800 ^0C. While the
crystallographic structure of the films depends solely on the T_d, their
microstructure and magnetization characteristics are decided by the growth
rate. At the higher G_r (~1A/sec) the L1_0 films have a maze-like structure
which converts to a continuous film as the t_F is increased from 20 to 50 nm.
The H_c of these films increases as the L1_0 phase fraction grows with T_d and
its orientation becomes out of the film plane. The evolution of microstructure
with T_d is remarkably different at lower growth rate (~0.4A /sec). Here the
structure changes from a self-similar fractal pattern to an assembly of
nano-dots as the T_d is raised from 700 to 800 ^0C, and is understood in terms
of the imbalance between strain and interfacial energies. MFM of such films
reveals no distinct domain walls within the nano-islands while a clear contrast
is seen between the islands of reversed magnetization. The simple picture of
coherent rotation of moment appears incompatible with the time dependence of
the remanent magnetization in these films. |
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| DOI: | 10.48550/arxiv.0803.0469 |