The electrical resistivity and thermopower S of Heusler compounds Fe 3Àx V x Al have been measured at the temperature range from 1.5 to 300 K at magnetic fields up to 15 T. The measurements of and S in the high temperature range up to 800 K have been performed. and S show a semiconducting behavior at high temperatures, and the obtained experimental energy gap increases almost linearly with increasing V concentration x. S is positive for x < 1:0 and negative for x ! 1:0 at all measured temperatures, indicating a drastic change of major carriers at x ¼ 1:0. The electron scattering due to the magnetic fluctuations of Fe clusters has a dominant effect on the behavior of of the magnetic compounds at low temperatures. On the other hand, S is not sensitive to the magnetic state and the external magnetic field, which is related to the energy dependence of magnetic scattering at the Fermi level.

We report on comprehensive measurements of the magnetic, transport, and thermal properties of the Heusler type compound Fe 2+x V 1−x Al at −0.05 x 020. We show that while stoichiometric Fe 2 VAl is a nonmagnetic semimetal (or narrow-gap semiconductor), a substitution on the nominal V-sites with the Fe atom leads to a ferromagnetic ground state above x = x c (∼0.05) with a rising Curie temperature T C and an ordered moment M s . At x = 0.1 and 0.2, the reduced value of the ratio M s /P eff 1, where P eff is the effective Curie-Weiss moment, together with the analysis of the magnetization data M(H ,T ), shows magnetism is itinerant. At a higher temperature T ∼ 60 K, a Schottky anomaly in specific heat C is indicated prominently at x > 0, while the anomaly is observable in the whole experimental range of x. At a lower temperature, an electronic component C/T in specific heat shows a divergence that arises at both x < 0 and x > 0. The resistivity-temperature curve ρ(T ) in the vicinity of the ferromagnetic quantum critical point, x ∼ 0.05, shows a non-Fermi liquid behavior, ρ ∼ T n (n ∼ 1), above H > 20 kOe.

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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The electrical resistivity ρ, the thermopower S and the magnetic susceptibility χ = M/B of the ternary compound EuNiGe 3 with the BaNiSn 3 -type structure have been measured at temperatures from 2 to 300 K. The measurements of ρ and S have been performed under pressures up to 1.8 GPa, together with ρ under pressures up to 8 GPa. With increasing temperature, the magnetic susceptibility χ shows a drastic increase, having a peak at the Néel temperature T N = 14 K and indicating the Curie-Weiss behavior at high temperature region. The effective magnetic moment of EuNiGe 3 is µ eff ≈ 7.7 µ B /Eu, indicating the 4f 7 (Eu 2+ ) electron configuration. The Néel temperature T N obtained from ρ(T ) and S (T ) curves increases linearly with increasing pressure. It is considered that the electron density of states of EuNiGe 3 in the vicinity of the Fermi energy has a small value and a weak energy dependence, and the Eu 2+ electronic configuration is stable.