A proposal for an alternative class of spin filter materials: Hybridization-induced high-<i>T</i>C ferromagnetic semiconductors CoVXAl (X = Ti, Zr, Hf)

Galanakis, I.; Özdoğan, K.; Şaşıoğlu, E.

doi:10.1063/1.4823820

Cited by 52 publications

(55 citation statements)

References 34 publications

(39 reference statements)

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“…[11][12][13][14][15][16] Although a large number of half-metallic Heusler compounds compounds has been studied, still novel properties are discovered among Heusler alloys, e.g. ferromagnetic or ferrimagnetic semiconducting behavior, [17][18][19][20] paving the way for diverse applications in spintronics/magnetoelectronics.…”

Section: Introductionmentioning

confidence: 99%

First-principles calculations of exchange interactions, spin waves, and temperature dependence of magnetization in inverse-Heusler-based spin gapless semiconductors

et al. 2015

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Employing first principles electronic structure calculations in conjunction with the frozen-magnon method we calculate exchange interactions, spin-wave dispersion, and spin-wave stiffness constants in inverse-Heusler-based spin gapless semiconductor (SGS) compounds Mn2CoAl, Ti2MnAl, Cr2ZnSi, Ti2CoSi and Ti2VAs. We find that their magnetic behavior is similar to the half-metallic ferromagnetic full-Heusler alloys, i.e., the intersublattice exchange interactions play an essential role in the formation of the magnetic ground state and in determining the Curie temperature, Tc. All compounds, except Ti2CoSi possess a ferrimagnetic ground state. Due to the finite energy gap in one spin channel, the exchange interactions decay sharply with the distance, and hence magnetism of these SGSs can be described considering only nearest and next-nearest neighbor exchange interactions. The calculated spin-wave dispersion curves are typical for ferrimagnets and ferromagnets. The spin-wave stiffness constants turn out to be larger than those of the elementary 3d-ferromagnets. Calculated exchange parameters are used as input to determine the temperature dependence of the magnetization and Tc of the SGSs. We find that the Tc of all compounds is much above the room temperature. The calculated magnetization curve for Mn2CoAl as well as the Curie temperature are in very good agreement with available experimental data. The present study is expected to pave the way for a deeper understanding of the magnetic properties of the inverse-Heusler-based SGSs and enhance the interest in these materials for application in spintronic and magnetoelectronic devices.

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Section: Introductionmentioning

confidence: 99%

First-principles calculations of exchange interactions, spin waves, and temperature dependence of magnetization in inverse-Heusler-based spin gapless semiconductors

et al. 2015

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“…A few halfmetallic FCFiMs have been synthesized, including Mn2RuxGa. 19,20 Recently, a number of quaternary Heusler compounds have been predicted by Galanakis et al to have spin-filter properties and Curie temperatures as high as TC = 2000 K. [21][22][23] Some of these LiMgPdSn-type Y-structure Heusler materials are also fully compensated with zero net moment -thus combining the magnetic advantages of a FCFiM with the spin-filter function, yet having a Curie temperature well above room temperature. One promising SF material is CrVTiAl, which is predicted to crystallize in a Y-type Heusler structure (space group 4 ̅ 3 ), as shown in Fig.…”

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confidence: 99%

Synthesis of low-moment CrVTiAl: A potential room temperature spin filter

Stephen

McDonald

Lejeune

et al. 2016

Applied Physics Letters

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The efficient production of spin-polarized currents at room temperature is fundamental to the advancement of spintronics. Spinfilter materials -semiconductors with unequal band gaps for each spin channel -can generate spin-polarized current without the need for spin-polarized contacts. In addition, a spin-filter material with zero magnetic moment would have the advantage of not producing strong fringing fields that would interfere with neighboring electronic components and limit the volume density of devices. The quaternary Heusler compound CrVTiAl has been predicted to be a zero-moment spin-filter material with a Curie temperature in excess of 1000 K. In this work, CrVTiAl has been synthesized with a lattice constant of a = 6.15 Å. Magnetization measurements reveal an exceptionally low moment of μ = 2.3 x 10 -3 µB/f.u. at a field of μ0H = 2 T, that is independent of temperature between T = 10 K and 400 K, consistent with the predicted zero-moment ferrimagnetism. Transport measurements reveal a combination of metallic and semiconducting components to the resistivity. Combining a zero-moment spin-filter material with nonmagnetic electrodes would lead to an essentially nonmagnetic spin injector. These results suggest that CrVTiAl is a promising candidate for further research in the field of spintronics.Future spintronic devices rely on the production of spin-polarized currents at room temperature.1-4 Spin-polarized currents can be generated several ways: by passing an unpolarized current through a ferromagnetic contact, using the spin-Hall or spin-Seebeck effects, by ballistic and hot electron injection, by employing spin-polarized materials such as half-metals, or using a spin-filter material. Half metals 5-9 and spin-filter (SF) materials 10,11 are especially suitable for spin injectors that are based on magnetic tunnel junctions (MTJs). 12 Furthermore, a spin injector using a spin-filter material is simpler, as it does not require magnetic electrodes.Spin-filter materials are magnetic semiconductors where the two spin states have unequal band gaps, shown in Fig. 1. When unpolarized electrons tunnel through a thin SF barrier they encounter a potential barrier that is lower for one spin state. As the tunneling probability increases exponentially with decreasing barrier height, the current for one spin direction will be much larger than for the other spin direction, thus creating a spin-polarized current. In practice, a spin filter is a simple MTJ-based device with the tunneling insulator replaced by the SF material, but more importantly, the magnetic MTJ electrodes are replaced by a nonmagnetic metal.13 This polarizing effect can be varied by applying a voltage to the spin-filter electrodes, hence creating a tunable spin valve. Spin filter devices have been fabricated with the magnetic semiconductor EuS 11,14 ; unfortunately, its low Curie temperature (TC = 16 K) limits its applicability.

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“…In the case of SFMs the most important property is the energy difference in the bottom of the conduction band for the two spin directions, the exchange splitting 2∆E ex , which corresponds to the difference of the barrier that spin up and spin down electrons confront when they tunnel through the SFM [57]. This exchange splitting for the SFMs under study is about 0.1-0.3 eV [26,27]. Thus, the energy quantities characterizing the SGSs and SFMs are relatively small.…”

Section: Motivation and Computational Detailsmentioning

confidence: 99%

“…Firstprinciples electronic band structure calculations have suggested that the ordered quaternary (CoV)YAl and (CrV)YAl Heusler compounds [24,25] -where Y stands for Ti, Zr, or Hf -are SFMs [26,27,28,29]. The former compounds are ferromagnetic semiconductors, while the latter ones are fully-compensated ferrimagnetic semiconductors, as they combine the existence of energy gaps in both spin directions to zero magnetization [26,27]. Both families of Heusler SFMs present high Curie temperatures well above the room temperature and, thus, are of interest for room-temperature spintronic/magnetoelectronic applications contrary to other well known SFMs [30,31,32,33].…”

Section: Introductionmentioning

confidence: 99%

A first-principles DFT+ GW study of spin-filter and spin-gapless semiconducting Heusler compounds

Taş

Şaşıoğlu

Friedrich

et al. 2017

Journal of Magnetism and Magnetic Materials

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Among Heusler compounds, the ones being magnetic semiconductors (also known as spin-filter materials) are widely studied as they offer novel functionalities in spintronic and magnetoelectronic devices. The spin-gapless semiconductors are a special case. They possess a zero or almost-zero energy gap in one of the two spin channels. We employ the GW approximation to simulate the electronic band structure of these materials. Our results suggest that in most cases the use of GW self energy instead of the usual density functionals is important to accurately determine the electronic properties of magnetic semiconductors.

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A proposal for an alternative class of spin filter materials: Hybridization-induced high-TC ferromagnetic semiconductors CoVXAl (X = Ti, Zr, Hf)

Cited by 52 publications

References 34 publications

First-principles calculations of exchange interactions, spin waves, and temperature dependence of magnetization in inverse-Heusler-based spin gapless semiconductors

First-principles calculations of exchange interactions, spin waves, and temperature dependence of magnetization in inverse-Heusler-based spin gapless semiconductors

Synthesis of low-moment CrVTiAl: A potential room temperature spin filter

A first-principles DFT+ GW study of spin-filter and spin-gapless semiconducting Heusler compounds

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