Local formation of a Heusler structure in CoFe–Al alloys

Wurmehl, S.; Jacobs, PJ; Swagten, Hjm Henk; Koopmans, B.; Maat, S.; Carey, M. J.; Childress, J. D.

doi:10.1063/1.3517490

Cited by 21 publications

(16 citation statements)

References 17 publications

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“…Thus, the strong enhancement of the spin signal by a factor of 10 is attributed to the efficient generation and detection of the spin current because CFA has a large spin polarization and the spin current backflow is significantly reduced. 26 The obtained spin polarization of the present CFA is close to the previously reported values, although the Al content and electrical resistivity are notably different, 19,20 which suggests that our CFA has a different crystal structure from those in the previous reports.…”

Section: Resultssupporting

confidence: 73%

“…It should be noted that the Al content was considerably different from the previously reported values. 19,20 A batch of conventional LSV structures with two CFA wires bridged by a nonmagnetic Cu wire was fabricated on a SiO 2 /Si substrate using electron beam lithography and the lift-off technique. Figure 2a shows a scanning electron microscope image of a representative device in our study.…”

Section: Methodsmentioning

confidence: 99%

“…19,20 This characteristic is an important advantage for preparing multiterminal functional lateral spin valve (LSV) structures because no specific substrate or thermal treatment is required during the sample fabrication process.…”

Section: Introductionmentioning

confidence: 99%

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Efficient thermal spin injection using CoFeAl nanowire

Itoh

Kimura

2014

NPG Asia Mater

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Nanoelectronic devices based on electron spin can overcome the physical limitations of the present semiconductor technology because of their low power consumption while exploiting the spin degree of freedom of electrons. Although enhancing the efficiency of generation of the spin current is imperative and a primary issue for the practical application of spin-based electronics, seamless device integration with the conventional complementary metal-oxide semiconductor technology is another important milestone for developing spin-based nanoelectronics. In particular, the preparation of nanosized, magnetic, multilayered structures with electrical connections to individual complementary metal-oxide semiconductor circuits significantly complicates the fabrication procedure of nanoelectronic devices. Thermal spin injection, which is a recently discovered unique characteristic of spin current, may be an innovative method for simplifying device integration without the need for electricity, namely wireless spintronics. However, the feasibility of using the thermal spin injection method is poor because of its extremely low-generation efficiency. Here, we demonstrate that a highly spin-polarized, ferromagnetic CoFeAl electrode with a favorable band structure has excellent properties for thermal spin injection. The spin-dependent Seebeck coefficient is approximately 70 lV K À1 , which facilitates highly efficient generation of the spin current from heat. The heat generates approximately 100 times more spin voltage than a conventional ferromagnetic injector at room temperature. This innovative demonstration may open a new route for spin-device integration and its applications.

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Section: Resultssupporting

confidence: 73%

Section: Methodsmentioning

confidence: 99%

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Efficient thermal spin injection using CoFeAl nanowire

Itoh

Kimura

2014

NPG Asia Mater

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“…[10][11][12][13][14][15][16][17][18] Such a local probe of structure and composition is very useful since compounds comprising elements from the same periodic row (e.g., Co and Fe) have very similar scattering factors for x-rays, and thus, x-ray diffraction (XRD) only may not be sufficient to resolve the structural ordering unambiguously in particular if both disorder and deviations from the 2:1:1 stoichiometry are present.…”

Section: 510mentioning

confidence: 99%

Nuclear magnetic resonance study of thinCo2FeAl0.5Si0.5Heusler films with varying thickness

et al. 2015

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Type, degree and evolution of structural order are important aspects for understanding and controlling the properties of highly spin polarized Heusler compounds, in particular with respect to the optimal film growth procedure. In this work, we compare the structural order and the local magnetic properties revealed by nuclear magnetic resonance (NMR) spectroscopy with the macroscopic properties of thin Co 2 FeAl 0.5 Si 0.5 Heusler films with varying thickness. A detailed analysis of the measured NMR spectra presented in this paper enables us to find a very high degree of L2 1 type ordering up to 81% concomitantly with excess Fe of 8 to 13% at the expense of Al and Si. We show, that the formation of certain types of order do not only depend on the thermodynamic phase diagrams as in bulk samples, but that the kinetic control may contribute to the phase formation in thin films. It is an exciting finding that Co 2 FeAl 0.5 Si 0.5 can form an almost ideal L2 1 structure in films though with a considerable amount of Fe-Al/Si off-stoichiometry.Moreover, the very good quality of the films as demonstrated by our NMR study suggests that the novel technique of off-axis sputtering technique used to grow the films sets stage for the optimized performance of Co 2 FeAl 0.5 Si 0.5 in spintronic devices.

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“…However, this is contrary to the reported results, 8 where the MR ratio rapidly falls to zero for devices annealed above 550 C. In order to have high MR ratios, the devices need both a high spin-polarized current 17 as well as smooth interfaces to maximize spin injection. 18,19 Let us consider the possibility of interdiffusion of Ag from the buffer layer into the Heusler film as explanation for the drop in MR of films annealed above 550 C. The current experimental parameter in our NMR experiment was chosen in such a way that the NMR signals stemming from the bulk are well resolved, but that NMR signals stemming from Co at the Co-Ag interfaces are hidden in the background signal. This is in particular true for Co nuclei located in an interdiffused region where different numbers of Ag atoms from the former smooth interface would have moved into the bulk film due to elevated annealing temperatures.…”

Section: Figmentioning

confidence: 99%