GMR in Heusler Type Alloys Fe2+xV1-xAl

Matsuda, Hiroko; Endo, Ken; Ooiwa, Kiyoshi; Iijima, M.; Takano, Yoshihiko; Mitamura, Hiroyuki; Goto, T.; Tokiyama, Masahumi; Arai, Jun

doi:10.1143/jpsj.69.1004

Cited by 29 publications

(31 citation statements)

References 14 publications

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“…The latter was corroborated by weak localization effects of the carriers in a random potential. 9 As shown in Fig. 5͑b͒, the sharp anomaly in ͑1 / ͒͑d / dT͒ is indicative of a bulk ferromagnetic transition at T = 33 K. In the ferromagnetic phase the resistivity follows a power law behavior ͑T͒ϳT n with n Х 3 / 2 ͓see inset to Fig.…”

Section: Electrical Resistivitymentioning

confidence: 84%

“…The presence of antisite Fe atoms on the nominal V site in the FeV 2 Al system brings about a simultaneous enhancement of the magnetization and resistivity at low temperatures. 7,9,10 This led to the claim that localized magnetic moments must be a crucial factor in the strong magnetic scattering of the conduction electrons responsible for the steep rise of the resistivity, the negative temperature coefficient of the resistivity, d / dT Ͻ 0 and a giant magnetoresistance at x Ͼ 0. Thus it is proposed that the steep rise of the electrical resistivity at lower temperature is not due to the energy gap but due to strong magnetic scattering.…”

Section: Introductionmentioning

confidence: 99%

“…Thus it is proposed that the steep rise of the electrical resistivity at lower temperature is not due to the energy gap but due to strong magnetic scattering. 7,9,10 Al poor Fe 2 VAl 1−␦ ͑␦ Ͼ 0͒, seems to undergo a ferromagnetic transition and shows metallic conduction below room temperature. 12 The Fe 2 VAl 1−␦ system at ␦ Ͼ 0 yields the opportunity to examine quantitatively not only the magnetic but also the transport and thermal properties within the framework of itinerant electron ferromagnetism, as established for intermetallic compounds, such MnSi and ZrZn 2 .…”

Section: Introductionmentioning

confidence: 99%

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Weak itinerant ferromagnetism in Heusler-typeFe2VAl0.95

et al. 2010

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Weak itinerant ferromagnetism in Sato, K.; Naka, T.; Taguchi, M.; Nakane, T.; Ishikawa, F.; Yamada, Y.; Takaesu, Y.; Nakama, T.; de Visser, A.; Matsushita, A. Published in:Physical Review B DOI:10.1103/PhysRevB.82.104408 Link to publicationCitation for published version (APA): Sato, K., Naka, T., Taguchi, M., Nakane, T., Ishikawa, F., Yamada, Y., ... Matsushita, A. (2010 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. We report measurements of the magnetic, transport, and thermal properties of the Heusler-type compound Fe 2 VAl 0.95 . We show that while stoichiometric Fe 2 VAl is a nonmagnetic semimetal a 5% substitution on the Al site with the 3d elements Fe and V atoms leads to a ferromagnetic ground state with a Curie temperature T C =33Ϯ 3 K and a small ordered moment s = 0.12 B / Fe in Fe 2 VAl 0.95 . The reduced value of the ratio s / p = 0.08, where p = 1.4 B / Fe is the effective Curie-Weiss moment, together with the analysis of the magnetization data M͑H , T͒, show magnetism is of itinerant nature. The specific heat shows an unusual temperature variation at low temperatures with an enhanced Sommerfeld coefficient, ␥ =12 mJ K −2 mol −1 . The resistivity, ͑T͒, is metallic and follows a power law behavior = 0 + AT n with n Ϸ 1.5 below T C . With applying pressure, T C decreases with the rate of ͑1 / T C ͒͑dT C / dP͒ = −0.061 GPa −1 . We conclude substitution on the Al site with Fe and V atoms results in itinerant ferromagnetism with a low carrier density.

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Section: Electrical Resistivitymentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Weak itinerant ferromagnetism in Heusler-typeFe2VAl0.95

et al. 2010

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“…Previously, the Mössbauer-spectra of Fe 2+x V 1−x Al have been interpreted in terms of fluctuating spins [14,15] and on basis of a "shell model" of magnetic ions immersed in a non-magnetic matrix [9]. The first model is inconsistent with the observation of bulk ferromagnetic ordering for Fe 2.1 V 0.9 Al and sc-Fe 2 VAl.…”

Section: )mentioning

confidence: 99%

“…Our structural investigation proves that slowly-cooled Fe 2 VAl, which we established on a microscopic scale to be ferromagnetically ordered below T C = 13K, is structurally better ordered than quenched material, for which we found evidence for substantial Al off-stoichiometry. For the quenched material the bulk properties [13] resemble the behaviour of "Kondo-insulating like" or "pseudogap" Fe 2 VAl [1,2,5,[9][10][11]16]; this suggests that the materials investigated in those works are Al deficient.As pointed out in Ref.[5], because of the electron count Al deficiency might have a strong effect on the actual position of the Fermi level E F in a pseudogap system. Specifically, it was argued that Al deficiency moves E F out of the centre of the pseudogap into the slopes, implying that Al deficient material should be more metallic than non-deficient one.…”

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confidence: 99%

Structure and magnetic order in Fe_2+xV_1−xAl

Maksimov

Baabe

Klauss

et al. 2001

J. Phys.: Condens. Matter

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Abstract:We present a detailed structural investigation via neutron diffraction of differently heat treated samples Fe 2 VAl and Fe 2+x V 1−x Al. Moreover, the magnetic behaviour of these materials is studied by means of µSR and Mössbauer-experiments. Our structural investigation indicates that quenched Fe 2 VAl, exhibiting the previously reported "Kondo insulating like" behaviour, is off-stoichiometric (6% ) in itsAl content. Slowly cooled Fe 2 VAl is structurally better ordered and stoichiometric, and the microscopic magnetic probes establish long range ferromagnetic order below T C = 13K, consistent with results from bulk experiments. The magnetic state can be modelled as being generated by diluted magnetic ions in a non-magnetic matrix. Quantitatively, the required number of magnetic ions is too large as to be explained by a model of Fe/V site exchange. We discuss the implications of our findings for the ground state properties of Fe 2 VAl, in particular with respect to the role of crystallographic disorder. ) IntroductionRecently, the magnetic phase diagram of the alloying series (Fe 1−x V x ) 3 Al has been the focus of various detailed studies [1,2]. In particular, Heuslertype Fe 2 VAl has been reported to exhibit a very unusual behaviour for an intermetallic compound, namely a semiconductor-like resistivity close to a magnetic instability [1]. This was interpreted in terms of Kondo-insulating behaviour, analogous to the system FeSi [3,4]. In contrast, optical conductivity studies provided evidence for a pseudogap in the density of states of 1 Fe 2 VAl of 0.1-0.2eV [5], a view supported by various band structure calculations [6][7][8]. Notably, no temperature dependence of the gap features has been detected in these studies, apparently contradicting a Kondo insulator scenario for Fe 2 VAl. However, the pseudogap scenario itself does not account for the unusual resistivity of Fe 2 VAl, as in the absence of magnetic correlations it should predict no or a positive metallic magnetoresistance, in conflict with experimental observations [2,9]. Therefore, in Ref. 5 it has been speculated that the (magneto)resistivity of Fe 2 VAl reflects a mixture of electron excitation processes over the pseudogap and spin dependent scattering from impurities.Independently, on basis of specific heat and NMR-experiments it has been demonstrated that in Fe 2 VAl crystallographic disorder, assumed to be present in form of atomic site exchange between Fe and V atoms, substantially affects the ground state properties of this compound [10,11]. In particular, the anomalous low temperature specific heat has been attributed to ferromagnetic clusters with a density of 0.003-0.004/unit cell, consistent with the results from NMR experiments. These works, as well, are in broad agreement with the results from band structure calculations, which predict that via Fe/V site exchange or crystallographic superstructure formation ferromagnetic clusters or long-range order might be generated in Fe 2 VAl [6][7][8]. Recently, it has been claimed that s...

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The Properties of Co2Cr1-xFexAl Heusler Compounds

Felser

Elmers

Fecher

2006

Half-Metallic Alloys

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The classical concept of band structure tuning as used for semiconductors by partly replacing one atom by a chemical neighbor without altering the structure is applied examplarily to the half-metallic ferromagnetic Heusler compound Co2Cr1−xFexAl. Band structure calculations are presented for ordered and disordered compounds. We present experimental and theoretical results. The connection between specific site disorder and the band structure is shown explicitly with particular emphasis on the half-metallic properties. Experimentally observed deviations from the ideal Heusler structure and from the simple Slater-Pauling rule for the magnetization are discussed in close relation to theoretical models. It has been found that the orbital magnetic moment and hence the spin-orbit coupling is important for the understanding of the half-metallicity. Experimental techniques which can be used to determine the electronic properties are described.

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GMR in Heusler Type Alloys Fe_2+xV_1-xAl

Cited by 29 publications

References 14 publications

Weak itinerant ferromagnetism in Heusler-typeFe2VAl0.95

Weak itinerant ferromagnetism in Heusler-typeFe2VAl0.95

Structure and magnetic order in Fe_2+xV_1−xAl

The Properties of Co2Cr1-xFexAl Heusler Compounds

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GMR in Heusler Type Alloys Fe2+xV1-xAl

Cited by 29 publications

References 14 publications

Weak itinerant ferromagnetism in Heusler-typeFe2VAl0.95

Weak itinerant ferromagnetism in Heusler-typeFe2VAl0.95

Structure and magnetic order in Fe2+xV1−xAl

The Properties of Co2Cr1-xFexAl Heusler Compounds

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Product

Resources

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GMR in Heusler Type Alloys Fe_2+xV_1-xAl

Structure and magnetic order in Fe_2+xV_1−xAl