Electrical and magnetic properties of thin films of the spin-filter material CrVTiAl

Abstract

The spin-filter material CrVTiAl is a promising candidate for producing highly spin-polarized currents at room temperature in a nonmagnetic architecture. Thin films of compensated-ferrimagnetic CrVTiAl have been grown and their electrical and magnetic properties have been studied. The resistivity shows two-channel semiconducting behavior with one disordered gapless channel and a gapped channel with activation energy ∆E= 0.1 -0.2 eV. Magnetoresistance measurements to B = 35 T provide values for the mobilities of the gapless channel, leading to an order of magnitude difference in the carrier effective masses, which are in reasonable accord with our density-functional-theory based results. The density of states and electronic band structure is computed for permutations of the four sublattices arranged differently along the (111) body diagonal, yielding metallic (Cr-V-Al-Ti), spin-gapless (Cr-V-Ti-Al) and spin-filtering (Cr-Ti-V-Al) phases. Robustness of the spin-gapless phase to substitutional disorder is also considered.FIG. 1. Schematic of a spin-filter device. The SFM is sandwiched between two nonmagnetic metallic contacts. As the barrier height for the electrons with different spin directions is different, the spin with the smaller band gap (barrier height) dominates the tunneling current.

High-Pressure Crystal Structure and Unusual Magnetoresistance of a Single-Component Molecular Conductor [Pd(dddt)2] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate)

“…Regarding the negative MR below 1 T, such behavior has been previously observed in weakly localized semiconductor CrVTiAl thin films [36] or multilayer graphene [37]. Interestingly, in the absence of the Dirac cone, the negative MR quickly disappeared above 10 K [36].…”

Pauli paramagnetism of cubic V3Al , CrVTiAl, and related 18-electron Heusler compounds with a group-13 element

“…Such alloys might be created by partial replacement of V by other transition metal elements, but to retain the desired balance of 18 electrons and zero net moment, a simultaneous replacement of two vanadium atoms by a chromium and a titanium is needed. This alloying approach could yield a ferrimagnetic spin structure with asymmetric spin states at the Fermi level, as predicted for CrVTiAl [13,22,23].…”

“…The CrVTiAl alloy was subsequently prepared in bulk [14,20,21] and thin film form [22,23]. It crystallizes in a cubic structure with a0 ≈ 610 pm and there is evidence of B2 atomic ordering [21,22].…”

Fully-Compensated Ferrimagnetic Spin Filter Materials within the Cr$\textit{M}\textit{N}$Al Equiatomic Quaternary Heusler Alloys

“…9,13,17 However, when synthesized in bulk form only a small component of an ordered L2 1 or Y phase was present. Similarly, the thin film was found in an SGS phase due to atomic swapping between magnetic sublattices, 15 illustrating the key role the arrangement of the atomic species across the four magnetic sub-lattices plays in the electronic and magnetic properties of the quaternary Heusler alloys. Therefore, further study of the Cr-based EQHA's is needed to find other atomic combinations which are immune to disorder effects.…”

“…Many half-metals, 10 spin gapless semiconductors (SGS), 11 and spin filter materials (SFM) 12 have been predicted, but only a few have been synthesized. [13][14][15][16] CrVTiAl, a member of the XX'YZ EQHA family, has been of particular interest due to its prediction to be a fully-compensated ferrimagnetic SFM with exceptional properties. 9,13,17 However, when synthesized in bulk form only a small component of an ordered L2 1 or Y phase was present.…”