Fourfold anisotropy and structural behavior of epitaxial hcp Co/GaAs(001) thin films

Gu, Erdan; Gester, M.; Hicken, R. J.; Daboo, C.; Tselepi, M.; Gray, S. J.; Bland, J. A. C.; Brown, L. M.; Thomson, Thomas; Riedi, P. C.

doi:10.1103/physrevb.52.14704

Cited by 49 publications

(49 citation statements)

References 19 publications

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“…Again, the main feature of this experimentally observed pattern is predicted in the calculated result shown in Fig. 1͑h͒, assuming the coexistence of bcc and hcp Co phases where the epitaxial relationships of hcp Co on GaAs͑001͒ are those proposed earlier, 5 i.e., ͑1210͓͒0001͔Co//͑001͓͒110͔GaAs and ͑1210͓͒0001͔Co//͑001͓͒110͔GaAs.…”

supporting

confidence: 59%

“…However, they did not compare their patterns with any theoretical calculations or with the patterns of known structures such as bcc Fe. Their conclusion was therefore questioned by Gu et al 5 Here we have unambiguously confirmed that Co grown on GaAs͑001͒ is in the bcc phase during the early stage of growth. This clears up the previous controversy.…”

supporting

confidence: 46%

“…Surprisingly, we see exactly the same pattern upon performing the experiment. This implies that the single-crystallike sixfold diffraction pattern might actually come from the two perpendicularly oriented hcp Co domains proposed earlier, 5 with ͓0001͔Co//͓110͔GaAs and ͓0001͔Co//͓110͔GaAs together. We show the calculated diffraction pattern in Fig.…”

mentioning

confidence: 99%

“…In fact, a fourfold in-plane magnetic anisotropy with the easy axes along the ͗100͘ rather than the ͗110͘ direction was observed by Blundell et al 4 Interestingly, it was later argued by Gu et al that Co films grown on GaAs͑001͒ were actually not bodycentered cubic but two-domain hexagonal close packed by which the fourfold magnetic anisotropy along the ͗100͘ direction could be explained by such a microstructure. 5 Obviously, the epitaxial structure of Co on GaAs͑001͒ and its magnetic anisotropy are still very controversial. In this work, we present a clear picture of the epitaxial growth of Co on GaAs͑001͒, which clears up the previous controversy about the structure of Co thin films on GaAs͑001͒.…”

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confidence: 99%

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In-plane magnetic anisotropy of bcc Co on GaAs(001)

Ding

Jing

et al. 1998

Phys. Rev. B

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Epitaxial growth of Co on GaAs͑001͒ and its in-plane magnetic anisotropy are studied using reflection high-energy electron diffraction, a high-resolution transmission electron microscope, and the magneto-optical Kerr effect. In the initial and final stages of growth, Co exists in single-crystalline body-centered-cubic ͑bcc͒ and hexagonal-closed-packed ͑hcp͒ phases, respectively, while in the middle stage the coexistence of the bcc and hcp structures is observed. For the bcc Co thin films on GaAs͑001͒, a fourfold in-plane magnetic anisotropy with easy axes along the ͗100͘ directions is realized and discussed. ͓S0163-1829͑98͒04915-7͔The 3d transition metals exist in a variety of crystallographic and magnetic phases. Thin-film growth of these materials on crystalline substrates allows the forces present at the interface to drive the film into specific crystalline structures. These structures may be in a thermodynamically stable phase, a known high-pressure or high-temperature phase, or even a phase not previously observed. They greatly increase the variety of magnetic materials by essentially making ''new'' materials from ''old'' elements. 1The epitaxial growth of Co films serves as a good example. It is known that the hexagonal-close-packed ͑hcp͒ and face-centered-cubic ͑fcc͒ structures are, respectively, stable and metastable phases of Co. The body-centered-cubic ͑bcc͒ structure, which does not occur in nature, was realized by Prinz with epitaxial growth on a GaAs͑110͒ substrate. However, it was later pointed out by Liu and Singh that bcc Co is not a true metastable phase but a force-induced phase. 3The in-plane magnetic anisotropy of such a bcc Co thin film on GaAs͑110͒ was further determined and a negative value for the cubic anisotropy constant K 1 was proposed.2 If this were true, a fourfold in-plane magnetic anisotropy with easy axes along the ͗110͘ direction would then be expected in the bcc Co films on GaAs͑001͒ substrates. In fact, a fourfold in-plane magnetic anisotropy with the easy axes along the ͗100͘ rather than the ͗110͘ direction was observed by Blundell et al. 4 Interestingly, it was later argued by Gu et al. that Co films grown on GaAs͑001͒ were actually not bodycentered cubic but two-domain hexagonal close packed by which the fourfold magnetic anisotropy along the ͗100͘ direction could be explained by such a microstructure.5 Obviously, the epitaxial structure of Co on GaAs͑001͒ and its magnetic anisotropy are still very controversial. In this work, we present a clear picture of the epitaxial growth of Co on GaAs͑001͒, which clears up the previous controversy about the structure of Co thin films on GaAs͑001͒. With the help of this clear picture, we prove that the bcc Co films on GaAs͑001͒ show a fourfold in-plane magnetic anisotropy.Co films were grown in a molecular-beam epitaxy ͑MBE͒ growth chamber connected with the VG-ESCALAB-5 electron spectrometer system. The Te-doped GaAs͑001͒ singlecrystal wafers were polished and treated by ordinary device cleaning process. The final substrate cleaning w...

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confidence: 59%

supporting

confidence: 46%

mentioning

confidence: 99%

mentioning

confidence: 99%

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In-plane magnetic anisotropy of bcc Co on GaAs(001)

Ding

Jing

et al. 1998

Phys. Rev. B

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“…Metastable bcc phase formation has been recognized for very thin Co [3][4][5] and Ni 6) films on GaAs single-crystal substrates of (100) and (110) orientations around RT deposited by molecular beam epitaxy (MBE). With increasing the thickness, most of the bcc-Co and the bcc-Ni crystals transformed into more stable hcp or fcc structure and the resulting films involved large volumes of hcp or fcc crystals.…”

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confidence: 99%

Structure Characterization of Fe, Co, and Ni Thin Films Epitaxially Grown on GaAs(111) Substrate

et al. 2018

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Fe, Co, and Ni films of 40 nm thickness are prepared on GaAs(111) single-crystal substrates at room temperature by using a radio-frequency magnetron sputtering system. The film growth behavior and the crystallographic properties are investigated by in-situ reflection high-energy electron diffraction and pole-figure X-ray diffraction. bcc single-crystals of (111) orientation are formed on the substrates for all the film materials, though the bcc structure is metastable for Co and Ni materials. The metastable structure is stabilized through hetero-epitaxial growth. Fe films possess bcc structure for the investigated thickness range. On the contrary, the bcc-Co and the bcc-Ni crystals, respectively, start to transform into hcp and fcc structures, as the thickness is increased beyond 2 nm. The phase transformations occur through atomic displacements from the close-packed planes of bcc(11 _ 0), bcc(1 _ 01), and bcc(011 _ ), which are perpendicular to the substrate surface, to hcp(0001) and fcc(111) close-packed planes. The crystallographic orientation relationships of hcp and fcc crystals with respect to bcc crystal are similar to the Kurdjumov-Sachs relationship.

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ChemInform Abstract: Ferromagnetic Metal/III‐V Semiconductor Hybrid Spintronic Devices

Wong

2008

ChemInform

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Fourfold anisotropy and structural behavior of epitaxial hcp Co/GaAs(001) thin films

Cited by 49 publications

References 19 publications

In-plane magnetic anisotropy of bcc Co on GaAs(001)

In-plane magnetic anisotropy of bcc Co on GaAs(001)

Structure Characterization of Fe, Co, and Ni Thin Films Epitaxially Grown on GaAs(111) Substrate

ChemInform Abstract: Ferromagnetic Metal/III‐V Semiconductor Hybrid Spintronic Devices

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