Heusler-alloy films for spintronic devices

Hirohata, Atsufumi; Sagar, James; Lari, Leonardo; Fleet, Luke; Lazarov, Vlado K.

doi:10.1007/s00339-013-7679-2

Cited by 78 publications

(33 citation statements)

References 18 publications

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“…This indicates that the films have at least the A2 phase after the annealing for 3 hours. A minor peak at 2θ ~ 43 º was appeared after 6 hours annealing which may be related to phase segregation as reported before [138] [143]. Additional analysis using TEM revealed that these films form the B2 and L2 1 phases as shown in [144].…”

Section: Film Characterisationsupporting

confidence: 62%

New Bandgap Measurement Technique for a Half-Metallic Ferromagnet

et al. 2014

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Spintronics is a new and emerging field in nanotechnology, which has been evolving rapidly. It aims to exploit the spin degree of freedom in order to realise advanced electronic devices. With the recent improvement in the storage media devices following to the discovery of giant magnetoresistance effect, it is envisioned that the electronic devices have several advantages over the conventional electronics in respect to the storage capacity, speed and power consumption. One avenue towards next generation spintronic devices is to develop half-metallic ferromagnets (HMFs) with 100% spin polarisation (P) and Curie temperature (T C ) above room temperature (RT). HMFs have unique properties, in which the majority spins have a metallic band structure, whereas the minority spins have a semiconducting band with the Fermi level (E F ) lying within an energy gap. P of HMFs has been predominantly estimated using Julliere's formula in a magnetic tunnel junction (MTJ) or measured by the Andreev reflection (AR) at low temperature. Both methods are very sensitive to the surface/interface spin polarisation.Alternative optical methods such as photoemission have also been employed. However, these methods require a complicated and expensive set-up. Therefore, it is of paramount importance to directly and easily measure the band-gap of HMFs.The main aim of this study is to develop a new technique to directly measure the band-gap (E g ) of HMFs at RT. For that, a simple experimental set-up has been designed This technique allows measuring E g of HMFs at RT for the first time. It can therefore be used to provide simple optimisation of growth conditions.iii

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Section: Film Characterisationsupporting

confidence: 62%

New Bandgap Measurement Technique for a Half-Metallic Ferromagnet

et al. 2014

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“…Co-based Heusler alloys have been attracting a lot of attention due to their predicted 100% spin polarization at the Fermi level, making them an ideal material of choice for many spintronic applications. [1][2][3][4][5] Among the half-metallic ferromagnetic (HMF) full Heusler alloys of the form X 2 YM (X,Y: transition metals, M: main group elements), Co 2 FeAl 0.5 Si 0.5 (CFAS) is of particular interest due to its high Curie temperature T C and giant tunnel magnetoresistance ratio at room temperature when used as an electrode in magnetic tunnel junctions. 6 The integration of HMF materials in existing largescale integrated circuits technologies could enable the development of fast and ultra-low power consumption Si-based spintronic devices.…”

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confidence: 99%

“…It is worth noting that along the [1][2][3][4][5][6][7][8][9][10] orientation of the fully ordered L2 1 phase, where Co, Fe, and Al/Si occupy the X, Y, and M sites, respectively, each atomic column is occupied by single species of Co, Fe, while Al/Si share the same atomic columns. In contrast to L2 1 , for films with B2 ordering, only the Co sub-lattice (populating the X sites) is fully ordered, whilst the Fe and Al/Si atomic species are intermixed (Y-M atomic sites mixing).…”

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confidence: 99%

The role of chemical structure on the magnetic and electronic properties of Co2FeAl0.5Si0.5/Si(111) interface

Kuerbanjiang

Nedelkoski

Kepaptsoglou

et al. 2016

Applied Physics Letters

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We show that Co2FeAl0.5Si0.5 film deposited on Si(111) has a single crystal structure and twin related epitaxial relationship with the substrate. Sub-nanometer electron energy loss spectroscopy shows that in a narrow interface region there is a mutual inter-diffusion dominated by Si and Co. Atomic resolution aberration-corrected scanning transmission electron microscopy reveals that the film has B2 ordering. The film lattice structure is unaltered even at the interface due to the substitutional nature of the intermixing. First-principles calculations performed using structural models based on the aberration corrected electron microscopy show that the increased Si incorporation in the film leads to a gradual decrease of the magnetic moment as well as significant spin-polarization reduction. These effects can have significant detrimental role on the spin injection from the Co2FeAl0.5Si0.5 film into the Si substrate, besides the structural integrity of this junction.

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“…half-metallic materials [5]. Several Co-based Heusler alloys such as Co 2 FeSi (CFS), Co 2 MnSi (CMS), Co 2 Fe(Si,Al) (CFAS), all predicted by density functional theory (DFT) calculations as 100% spin-polarized materials, have been already implemented in a number of heterostructured spintronic devices [6][7][8][9][10][11][12][13][14]. We would like to note that the correlation between the calculated spin-polarization (SP) by DFT and the measured SP indirectly through transport device parameters or optical methods is not straightforward and requires careful consideration of several phenomena that arise from temperature effects, such as magnon and phonon effects etc [15].…”

Section: Introductionmentioning

confidence: 99%

Controlling the half-metallicity of Heusler/Si(1 1 1) interfaces by a monolayer of Si–Co–Si

Nedelkoski

Kepaptsoglou

Ghasemi

et al. 2016

J. Phys.: Condens. Matter

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By using first-principles calculations we show that the spin-polarization reverses its sign at atomically abrupt interfaces between the half-metallic Co2(Fe,Mn)(Al,Si) and Si(1 1 1). This unfavourable spin-electronic configuration at the Fermi-level can be completely removed by introducing a Si–Co–Si monolayer at the interface. In addition, this interfacial monolayer shifts the Fermi-level from the valence band edge close to the conduction band edge of Si. We show that such a layer is energetically favourable to exist at the interface. This was further confirmed by direct observations of CoSi2 nano-islands at the interface, by employing atomic resolution scanning transmission electron microscopy.

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Heusler-alloy films for spintronic devices

Cited by 78 publications

References 18 publications

New Bandgap Measurement Technique for a Half-Metallic Ferromagnet

New Bandgap Measurement Technique for a Half-Metallic Ferromagnet

The role of chemical structure on the magnetic and electronic properties of Co2FeAl0.5Si0.5/Si(111) interface

Controlling the half-metallicity of Heusler/Si(1 1 1) interfaces by a monolayer of Si–Co–Si

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