Pseudogap state and strong scattering of current carriers by local spin moments as mechanisms for the semiconducting properties of near-stoichiometric iron-vanadium-aluminum alloys

Abstract

New experimental evidence is obtained on the physical nature of the semiconducting properties of Fe 2Àx V 1þx Al alloys with near-stoichiometric (x ¼ 0) compositions. We examine the low-temperature thermal emf of two alloys: one is enriched in vanadium and exhibits a pseudogap in the electron density of states at the Fermi energy, while in the other, which is depleted in vanadium, the scattering of electrons by localized spins has a stronger influence. The experimental temperature dependences of the thermal emf at low temperatures display some characteristic anomalies that are observed here for the first time and are manifestations of these two effects. Existing theory is used to interpret the anomalous contributions of both effects (types), determine their characteristic parameters, and establish the conditions under which they appear in V-depleted and V-enriched alloys. Data on the thermal emf in magnetic fields show that that the thermal emf decreases substantially as the magnetic field is increased, confirming the key role of the mechanism of current carrier scattering by localized moments. V C 2013 American Institute of Physics. [http://dx.

Unusual Kinetic Properties of Usual Heusler Alloys

“…It turned out that pseudogap-related anomalies are observed as well in other kinetic and magnetic characteristics of alloys based on Fe2VAl [13,14,[41][42][43]. In [41], the thermoelectric power α(T) of the Fe1.9V1.1Al compound was studied and it was found that at T < 20 K, a large non-monotonic contribution α(T) is observed, the presence of which can be explained by the existence of a pseudogap near the Fermi level EF. The thermal conductivity and heat capacity of Heusler compounds based on Fe2VAl were studied in [13,14,42].…”

Magnetic and thermal properties of alloys close in composition to the spin gapless semiconductor Mn2CoAl

“…1 and 2 and references therein). The Heusler compounds family has more than 1500 alloys which exhibit various functional properties, i.e., magnetocaloric effect, 3,4 unusual thermal, 5,6 thermoelectric 7 and semiconductor [8][9][10] characteristics, properties of half-metallic ferromagnets 11,12,18 and spin gapless semiconductors. 13,14,19 The so-called full and inverse Heusler alloys are studied the most.…”