Structural and magnetic properties of epitaxial thin films of the equiatomic quaternary CoFeMnSi Heusler alloy

Bainsla, Lakhan; Yilgin, Resul; Okabayashi, Jun; Ono, A.; Suzuki, Kazuya; Mizukami, Shigemi

doi:10.1103/physrevb.96.094404

Cited by 58 publications

(25 citation statements)

References 41 publications

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“…The Cr buffer layer was annealed in situ at 700 • C for 1 h to obtain a flat surface with (001) orientation. 27 The CoFeCrAl layer was deposited on the substrate using an alloy target, with the film composition of Co 25.5 kOe was applied along the incident polarized soft x-ray. The extent of circular polarization was evaluated to be 85%.…”

Section: Experimental and Theoretical Calculation Proceduresmentioning

confidence: 99%

“…Previously, we reported the structural and magnetic properties of epitaxial films of CoFeMnSi, which is another EQHA that is an SGS candidate. The films grown on a Cr buffer had a B2 as well as partial L2 1 orderings, 27 and their MTJs exhibited TMR ratios of more than 500% at 10 K, suggesting half-metallic electronic characteristics. 8 Different from CoFeMnSi, only B2-ordered CoFeCrAl films were obtained in this study, despite the similar fabrication conditions and vacuum deposition apparatus.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic tunnel junctions with a B2 -ordered CoFeCrAl equiatomic Heusler alloy

Tsuchiya

Roy

Elphick

et al. 2019

Phys. Rev. Materials

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The equiatomic quaternary Heusler alloy CoFeCrAl is a candidate material for spin-gapless semiconductors (SGSs). However, to date, there have been no experimental attempts at fabricating a junction device. This paper reports a fully epitaxial (001)-oriented MgO barrier magnetic tunnel junction (MTJ) with CoFeCrAl electrodes grown on a Cr buffer. X-ray and electron diffraction measurements show that the (001) CoFeCrAl electrode films with atomically flat surfaces have a B2-ordered phase. The saturation magnetization is 380 emu/cm 3 , almost the same as the value given by the Slater-Pauling-like rule, and the maximum tunnel magnetoresistance ratios at 300 K and 10 K are 87% and 165%, respectively. Cross-sectional electron diffraction analysis shows that the MTJs have MgO interfaces with fewer dislocations. The temperature-and bias-voltagedependence of the transport measurements indicates magnon-induced inelastic electron tunneling overlapping with the coherent electron tunneling. X-ray magnetic circular dichroism (XMCD) measurements show a ferromagnetic arrangement of the Co and Fe magnetic moments of B2ordered CoFeCrAl, in contrast to the ferrimagnetic arrangement predicted for the Y -ordered state possessing SGS characteristics. Ab-initio calculations taking account of the Cr-Fe swap disorder qualitatively explain the XMCD results. Finally, the effect of the Cr-Fe swap disorder on the ability for electronic states to allow coherent electron tunneling is discussed.

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Section: Experimental and Theoretical Calculation Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Magnetic tunnel junctions with a B2 -ordered CoFeCrAl equiatomic Heusler alloy

Tsuchiya

Roy

Elphick

et al. 2019

Phys. Rev. Materials

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“…New materials are likely to be identified, for which EG, Δ, confinement behaviour, strain behaviour, etc., would be addressed for each material separately. 15,16,35 We now describe the operation of the actual spin-MOSFET device. As a bandstructure example we adopt the one from Fig.…”

Section: Figure 2ementioning

confidence: 99%

“…even in the most complex quaternary alloys,35,59 which increases their technological appeal. The proposed device could be a promising candidate for the realization of spin-MOSFETs with room temperature operation and large spin polarization robustness that combine logic and memory functionalities.…”

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confidence: 99%

Simulation study of ballistic spin-MOSFET devices with ferromagnetic channels based on some Heusler and oxide compounds

Graziosi

Neophytou

2018

Journal of Applied Physics

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Newly emerged materials from the family of Heuslers and complex oxides exhibit finite bandgaps and ferromagnetic behavior with Curie temperatures much higher than even room temperature. In this work, using the semiclassical top-of-the-barrier FET model, we explore the operation of a spin-MOSFET that utilizes such ferromagnetic semiconductors as channel materials, in addition to ferromagnetic source/drain contacts.Such a device could retain the spin polarization of injected electrons in the channel, the loss of which limits the operation of traditional spin transistors with non-ferromagnetic channels. We examine the operation of four material systems that are currently considered some of the most prominent known ferromagnetic semiconductors, three Heusler-type alloys (Mn2CoAl, CrVZrAl, CoVZrAl) and one from the oxide family (NiFe2O4). We describe their bandstructures by using data from DFT calculations. We investigate under which conditions high spin polarization and significant ION/IOFF ratio, two essential requirements for the spin-MOSFET operation, are both achieved. We show that these particular Heusler channels, in their bulk form, do not have adequate bandgap to provide high ION/IOFF ratios, and have small magnetoconductance compared to state-of-the-art devices. However, with confinement into ultra-narrow sizes down to a few nanometers, and by engineering their spin dependent contact resistances, they could prove promising channel materials for the realization of spin-MOSFET transistor devices that offer combined logic and memory functionalities. Although the main compounds of interest in 2 this paper are Mn2CoAl, CrVZrAl, CoVZrAl, and NiFe2O4 alone, we expect that the insight we provide is relevant to other classes of such materials as well.

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“…So far, a huge number of studies of PMA have been reported, which have been originated from the d - d or d - p electron orbital hybridizations of ferromagnetic layer and noble metal (Pt, Pd) or oxygen of oxides at the interfaces [ 9 – 12 ]. Moreover, Heusler quaternary compound CoFeMnSi (CFMS) has been proved to be a spin gapless semiconductor (SGS) [ 13 – 15 ], which is also very sensitive to the external field [ 16 ], showing the potential advantages of being a sensor. In this work, the Ta/Pd/CoFeMnSi/MgO/Pd-structured films were designed to achieve the strong PMA by the interfacial effect, and the hydrogenation-induced magnetic change was explored.…”

Section: Introductionmentioning

confidence: 99%

Perpendicular Magnetic Anisotropy and Hydrogenation-Induced Magnetic Change of Ta/Pd/CoFeMnSi/MgO/Pd Multilayers

Zhang

Chen

et al. 2018

Nanoscale Res Lett

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The perpendicular magnetic anisotropy (PMA) has been achieved in Ta/Pd/CoFeMnSi (CFMS)/MgO/Pd film, in which the Heusler compound CoFeMnSi is one of the most promising candidates for spin gapless semiconductor (SGS). The strong PMA, with the effective anisotropy constant Keff of 5.6 × 105 erg/cm3 (5.6 × 104 J/m3), can be observed in the Ta/Pd/CFMS (2.3 nm)/MgO (1.3 nm)/Pd films annealed at 300 °C. In addition, it was found that the magnetic properties of Ta/Pd/CFMS/MgO/Pd films are sensitive to hydrogen (H2) under a weak magnetic field (< 30 Oe), whose residual magnetization (Mr) decreased from 123.15 to 30.75 emu/cm3 in the atmosphere with H2 concentration of 5%.

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Structural and magnetic properties of epitaxial thin films of the equiatomic quaternary CoFeMnSi Heusler alloy

Cited by 58 publications

References 41 publications

Magnetic tunnel junctions with a B2 -ordered CoFeCrAl equiatomic Heusler alloy

Magnetic tunnel junctions with a B2 -ordered CoFeCrAl equiatomic Heusler alloy

Simulation study of ballistic spin-MOSFET devices with ferromagnetic channels based on some Heusler and oxide compounds

Perpendicular Magnetic Anisotropy and Hydrogenation-Induced Magnetic Change of Ta/Pd/CoFeMnSi/MgO/Pd Multilayers

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