Experimental validation of the anomalies in the electron density of states in semiconductor iron-vanadium-aluminum alloys

Abstract

The temperature dependences of the resistivity, Hall coefficient, and magnetic susceptibility of iron-vanadium-aluminum alloys have been investigated. It has been established that the alloy Fe1.9V1.1Al exhibits semiconductor behavior for the method used to obtain uniform alloys. It is shown that at temperatures below 30K the semiconductor alloy possesses the characteristic low-temperature scale of the dependences observed, which could be responsible for the appearance of a narrow pseudogap in the electron density of states. A simple theoretical description of the effects of a pseudogap is proposed. A consistent fit of the theoretical to the experimental relations made it possible to determine the effective width of the pseudogap (∼1MeV) and its relative depth (∼102).

Electrical and Magnetic Properties of Selected Fe-Based High Entropy Alloys

“…The plots of lnρ versus 1/T (ρ resistivity, T temperature) for the data in the temperature interval 150300 K (the temperature range depends on the sample) becomes almost linear, and an energy gap ∆ of about 110 meV is tentatively obtained for samples: 2-am, 1-ms and 2-ms, assuming that they are semiconducting. The obtained values of the energy gap are the same as estimated by Okulov et al [23], but signicantly smaller (by one order) than ones obtained for Heusler-type alloys [19,20,24,25]. The small values of ∆ suggest that the densities of states of the investigated samples exhibit a pseudo-gap rather than a real energy gap.…”

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

“…A similar effect, also seen in Ref. 4, is observed in the temperature dependences of the Hall current carrier concentrations and magnetic susceptibility. Thus, the origin of this effect should be ascribed to features of the electron density of states in the neighborhood of the Fermi energy, rather than to scattering.…”

“…The existence, in this alloy, of two temperature regions with highly different scales for the temperature dependence of the resistivity has been established previously. 4 The transition from a comparatively sharp to a smoother variation in q(T) near 20 K can be seen clearly in the upper inset to Fig. 1.…”

“…This line of reasoning has been discussed previously. 4 A simple theoretical description of the contribution of a pseudogap to the temperature dependences can be obtained, without considering detailed features of its shape, under the assumption that the temperature exceeds the scales associated with these features. Also neglecting the role of the anisotropy in the electron energy, we write the conductivity in the form of an integral with respect to e of the function r(e) with the derivative with respect to e of the Fermi energy, where r(e) is the conductivity of the electron system at a Fermi energy equal to e. Then the contribution of the pseudogap can be described by the appropriate part of the FIG.…”

Spin gapless semiconducting behavior in equiatomic quaternary CoFeMnSi Heusler alloy

“…Carrier concentration of the CFMS alloy is calculated from the Hall coefficient (R H ) measurements. The temperature-independent carrier concentration (n) is observed in the temperature range from 5 to 300 K, which is typical of spin gapless semiconductors [2,22]; carrier concentration of 4 × 10 19 cm −3 is observed at 300 K, which is comparable to that observed for HgCdTe (10 15 −10 17 cm −3 ), Mn 2 CoAl (10 17 cm −3 ), and Fe 2 VAl (10 21 cm −3 ) [23]. The physical reasons for the nearly temperature-independent carrier concentration in gapless semiconductors as compared to the exponential dependence in the case of conventional semiconductors are well established [22,24].…”