Spin polarization and Gilbert damping of Co2Fe(GaxGe1−x) Heusler alloys
TL;DR: The spin polarization of ferromagnetic Heusler alloys, Co 2 Fe(Ga x Ge 1−x ) ( x ǫ = 0, 0.75, and 1), is investigated by point contact Andreev reflection (PCAR) measurements as discussed by the authors.
About: This article is published in Acta Materialia.The article was published on 2012-10-01. It has received 105 citations till now. The article focuses on the topics: Half-metal & Spin polarization.
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TL;DR: In this article, the linewidth of a series of Permalloy films with thicknesses of 50 and 100nm was measured using linear function of frequency, with a slope that corresponds to a nominal Landau-Lifshitz phenomenological damping parameter α value of 0.007 and zero frequency intercepts in the 160-320A∕m (2-4Oe) range.
Abstract: Stripline (SL), vector network analyzer (VNA), and pulsed inductive microwave magnetometer (PIMM) techniques were used to measure the ferromagnetic resonance (FMR) linewidth for a series of Permalloy films with thicknesses of 50 and 100nm. The SL-FMR measurements were made for fixed frequencies from 1.5to5.5GHz. The VNA-FMR and PIMM measurements were made for fixed in-plane fields from 1.6to8kA∕m (20–100Oe). The results provide a confirmation, lacking until now, that the linewidths measured by these three methods are consistent and compatible. In the field format, the linewidths are a linear function of frequency, with a slope that corresponds to a nominal Landau-Lifshitz phenomenological damping parameter α value of 0.007 and zero frequency intercepts in the 160–320A∕m (2–4Oe) range. In the frequency format, the corresponding linewidth versus frequency response shows a weak upward curvature at the lowest measurement frequencies and a leveling off at high frequencies.
430 citations
TL;DR: In this paper, a quaternary Heusler structure with different structural symmetries (space group F-43m, #216) was obtained for half-metallic ferromagnetic (HMF) materials.
Abstract: Half-metallic ferromagnetic (HMF) materials show high spin polarization and are therefore interesting to researchers due to their possible applications in spintronic devices. In these materials, while one spin sub band has a finite density of states at the Fermi level, the other sub band has a gap. Because of their high Curie temperature (TC) and tunable electronic structure, HMF Heusler alloys have a special importance among the HMF materials. Full Heusler alloys with the stoichiometric composition X2YZ (where X and Y are the transition metals and Z is a sp element) have the cubic L21 structure with four interpenetrating fcc sublattices. When each of these four fcc sublattices is occupied by different atoms (XX′YZ), a quaternary Heusler structure with different structural symmetries (space group F-43m, #216) is obtained. Recently, these equiatomic quaternary Heusler alloys (EQHAs) with 1:1:1:1 stoichiometry have attracted a lot of attention due to their superior magnetic and transport properties. A speci...
220 citations
University of Hamburg1, Ohio State University2, Taras Shevchenko National University of Kyiv3, ETH Zurich4, Radboud University Nijmegen5, University of York6, University of Nebraska–Lincoln7, Spanish National Research Council8, Trinity College, Dublin9, National Institute of Standards and Technology10, Université Paris-Saclay11, University of Mainz12, Free University of Berlin13, Fritz Haber Institute of the Max Planck Society14, Daegu Gyeongbuk Institute of Science and Technology15
TL;DR: The very relevant advances in the field of magnetism research during the past years make yet another Magnetism Roadmap a very sensible and timely endeavour, and allow its authors and readers to take another broad-based, but concise look at the most significant developments in magnetism.
Abstract: Following the success and relevance of the 2014 and 2017 Magnetism Roadmap articles, this 2020 Magnetism Roadmap edition takes yet another timely look at newly relevant and highly active areas in magnetism research The overall layout of this article is hereby unchanged, given that it is very suitable to convey the most relevant aspects of today's magnetism research in a wide variety of sub-fields to a broad readership Again, a different group of experts has been selected, representing both the novelty of new research areas as well as the desire to incorporate different voices and viewpoints The latter is especially relevant for this type of article, in which one's field of expertise has to be accommodated on two printed pages only, so that personal selection preferences are naturally rather more visible than in other types of articles Most importantly, the very relevant advances in the field of magnetism research during the past years make yet another Magnetism Roadmap a very sensible and timely endeavour, and allow its authors and readers to take another broad-based, but concise look at the most significant developments in magnetism, their precise status, their challenges and their anticipated future developments
153 citations
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TL;DR: In this paper, a quaternary Heusler structure with different structural symmetry is obtained for half-metallic ferromagnetic (HMF) alloys with the stoichiometric composition X2YZ, where X and Y are transition metals and Z is a sp element.
Abstract: Half-metallic ferromagnetic (HMF) materials show high spin polarization and are therefore interesting to researchers due to their possible applications in spintronic devices. In these materials, while one spin sub band has a finite density of states at the Fermi level, the other sub band has a gap. Because of their high Curie temperature and tunable electronic structure, HMF Heusler alloys have a special importance among the HMF materials. Full Heusler alloys with the stoichiometric composition X2YZ (where X and Y are the transition metals and Z is a sp element) have the cubic structure with four interpenetrating fcc sublattices. When each of these four fcc sublattices is occupied by different atoms, a quaternary Heusler structure with different structural symmetry is obtained. Recently, these equiatomic quaternary Heusler alloys (EQHAs) with 1:1:1:1 stoichiometry have attracted a lot of attention due to their superior magnetic and transport properties.
142 citations
TL;DR: Heusler alloys are theoretically predicted to become half-metals at room temperature (RT) and by employing these ferromagnetic alloy films in a spintronic device, efficient spin injection into a non-magnetic material and large magnetoresistance are also discussed.
126 citations
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...174 [109] 829 (bulk) [45] 60 [62] [114]...
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...0 [144] ~ 0,15 [144] 1100 [62] 42 [148] [153]...
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...210 [109] 905 (bulk) [45] 58 [62] [105]...
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References
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TL;DR: A simple derivation of a simple GGA is presented, in which all parameters (other than those in LSD) are fundamental constants, and only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked.
Abstract: Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. [S0031-9007(96)01479-2] PACS numbers: 71.15.Mb, 71.45.Gm Kohn-Sham density functional theory [1,2] is widely used for self-consistent-field electronic structure calculations of the ground-state properties of atoms, molecules, and solids. In this theory, only the exchange-correlation energy EXC › EX 1 EC as a functional of the electron spin densities n"srd and n#srd must be approximated. The most popular functionals have a form appropriate for slowly varying densities: the local spin density (LSD) approximation Z d 3 rn e unif
146,533 citations
TL;DR: In this article, the authors improved the description of both electron energy loss spectra and parameters characterizing the structural stability of the material compared with local spin density functional theory by taking better account of electron correlations in the $3d$ shell of metal ions in nickel oxide.
Abstract: We demonstrate how by taking better account of electron correlations in the $3d$ shell of metal ions in nickel oxide it is possible to improve the description of both electron energy loss spectra and parameters characterizing the structural stability of the material compared with local spin density functional theory.
10,045 citations
TL;DR: The band structure of Mn-based Heusler alloys of the crystal structure (MgAgAs type) has been calculated with the augmented-spherical-wave method.
Abstract: The band structure of Mn-based Heusler alloys of the $C{1}_{b}$ crystal structure (MgAgAs type) has been calculated with the augmented-spherical-wave method. Some of these magnetic compounds show unusual electronic properties. The majority-spin electrons are metallic, whereas the minority-spin electrons are semiconducting.
3,851 citations
Journal Article•
TL;DR: The theory of ferromagnetic resonance absorption was extended in this paper to include the effect of the shape of the specimen and, in the case of a single crystal, of crystal orientation.
Abstract: The theory of ferromagnetic resonance absorption previously developed is extended to include the effect of the shape of the specimen and, in the case of a single crystal, the effect of crystal orientation. The resonance condition may be written ${\ensuremath{\omega}}_{0}=\ensuremath{\gamma}{H}_{\mathrm{eff}}$, where ${H}_{\mathrm{eff}}$ is equal to ${(\mathrm{BH})}^{\frac{1}{2}}$ for a plane surface, $H+2\ensuremath{\pi}M$ for a long circular cylinder, and $H$ for a sphere; the latter two values apply only to the situation in which the eddy current skin depth is large in comparison with the radius of the specimen. In the case of an uniaxial crystal with the axis parallel to the static magnetic field, the value of $H$ to be used in the resonance conditions is increased by $\frac{2K}{M}$, where $K$ is the anisotropy constant. The case of a cubic crystal is also considered. A detailed discussion of macroscopic eddy current effects is given, and it is shown that the usual eddy current losses do not introduce damping terms into the expression for the permeability, when properly interpreted.
1,816 citations
TL;DR: In this article, the full-potential screened Korringa-Kohn-Rostoker method was used to study the half-metallic properties of Co, Fe, Rh, and Ru.
Abstract: Using the full-potential screened Korringa-Kohn-Rostoker method we study the full-Heusler alloys based on Co, Fe, Rh, and Ru. We show that many of these compounds show a half-metallic behavior; however, in contrast to the half-Heusler alloys the energy gap in the minority band is extremely small due to states localized only at the Co (Fe, Rh, or Ru) sites which are not present in the half-Heusler compounds. The full-Heusler alloys show a Slater-Pauling behavior and the total spin magnetic moment per unit cell ${(M}_{t})$ scales with the total number of valence electrons ${(Z}_{t})$ following the rule ${M}_{t}{=Z}_{t}\ensuremath{-}24.$ We explain why the spin-down band contains exactly 12 electrons using arguments based on group theory and show that this rule holds also for compounds with less than 24 valence electrons. Finally we discuss the deviations from this rule and the differences compared to the half-Heusler alloys.
1,688 citations