We employ ab-initio electronic structure calculations to study 60 LiMgPdSn-type (also known as LiMgPdSb-type) quaternary Heusler compounds. All compounds obey the Slater-Pauling rule with diverse electronic and magnetic properties. 41 compounds are found to be half-metals, 8 spingapless semiconductors, and 9 semiconductors. CoVTiAl and CrVTiAl compounds are identified as ferromagnetic and antiferromagnetic semiconductors, respectively, with large energy gaps in both spin directions. All magnetic compounds are expected to have high Curie temperatures making them suitable for spintronics/magnetoelectronics applications. V C 2013 AIP Publishing LLC.

We present extensive first-principles calculations on the inverse full-Heusler compounds having the chemical formula X2YZ where (X = Sc, Ti, V, Cr or Mn), (Z = Al, Si or As) and the Y ranges from Ti to Zn. Several of these alloys are identified to be half-metallic magnets. We show that the appearance of half-metallicity is associated in all cases to a Slater-Pauling behavior of the total spin-magnetic moment. There are three different variants of this rule for the inverse Heusler alloys depending on the chemical type of the constituent transition-metal atoms. Simple arguments regarding the hybridization of the d -orbitals of neighboring atoms can explain these rules. We expect our results to trigger further experimental interest on this type of half-metallic Heusler compounds. PACS numbers: 75.50.Cc, 75.30.Et, 71.15.Mb The rise of nanotechnology and nanoscience during the last decade brought to the center of scientific research new phenomena and materials. Spintronics and magnetoelectronics compose one of the most rapidly expanding field in nanoscience. 1 Half-metallic magnetic compounds play a crucial role in this development. 2 These materials present usual metallic behavior for the one spin direction while an energy gap in the band structure is present in the other spin direction similarly to semiconductors. 3,4 The possibility of creating 100% spin-polarized current has triggered the interest on such compounds. 5 De Groot and collaborators in 1983 have initially suggested based on electronic structure calculations that NiMnSb, a semi-Heusler alloy, is a halfmetal 6 and since then several half-metallic compounds have been discovered. 7 Several aspects concerning the implementation of half-metallic alloys in realistic devices, like tunnelling magnetic junctions or giant magnetoresistive junctions and spin-injectors, have been discussed in literature. [8][9][10] The family of Heusler alloys incorporates more than 1000 members almost all crystalizing in a close-packed cubic structure similar to the binary semiconductors. 11 Most of them are metals exhibiting diverse magnetic phenomena. The lattice is a f.c.c. with four equidistant sites as basis along the diagonal of the unit cell. 3 There are two families of Heusler alloys. The semi-(or half-)Heuslers have the chemical formula XYZ where the sequence of the sites is X-Y-void-Z. The X and Y are transitionmetal elements and Z is a sp-element and the structure is known as the C1 b lattice. The second subfamily consists the full-Heusler compounds with the chemical formula X 2 YZ. When the valence of the X is larger than Y, the atomic sequence is X-Y-X-Z and the structure is the well known L2 1 one with prototype Cu 2 MnAl. 12 When the valence of the Y elements is the largest, the compounds crystallize in the so-called XA structure, where the sequence of the atoms is X-X-Y-Z and the prototype is Hg 2 TiCu. 12 The latter alloys are also known as inverse Heusler compounds. Several inverse Heuslers have been studied using first-principles electronic structure calculat...

We employ ab-initio electronic structure calculations to search for spin gapless semiconductors, a recently identified new class of materials, among the inverse Heusler compounds. The occurrence of this property is not accompanied by a general rule and results are materials specific. The six compounds identified show semiconducting behavior concerning the spin-down band structure and in the spin-up band structure the valence and conduction bands touch each other leading to 100% spin-polarized carriers. Moreover these six compounds should exhibit also high Curie temperatures and thus are suitable for spintronics applications.

Half-metallic antiferromagnets are the ideal materials for spintronic applications since their zero magnetization leads to lower stray fields and thus tiny energy losses. Starting from the Mn2VAl and Mn2VSi alloys we substitute Co and Fe for Mn and we show by means of first-principle electronic structure calculations that the resulting compounds are ferrimagnets. When the total number of valence electrons reaches the magic number of 24 the Fe-doped compounds are semi-metals and thus non-magnetic while the Co-doped ones show the desirable half-metallic antiferromagnetic character. The compounds are very likely to be synthesized experimentally since the parent compounds, Mn2VAl and Co2VAl, have been already grown in the Heusler L21 lattice structure.

Abstract.Using a state-of-the-art full-potential electronic structure method within the local spin density approximation, we study the electronic and magnetic structure of Mn 2 V-based full Heusler alloys: Mn 2 VZ (Z=Al, Ga, In, Si, Ge, and Sn). We show that small expansion of the calculated theoretical equilibrium lattice constants restores the half-metallic ferrimagnetism in these compounds. Moreover a small degree of disorder between the V and Z atoms, although iduces some states within the gap, it preserves the Slater-Pauling behaviour of the spin magnetic moments and the alloys keep a high degree of spin-polarisation at the Fermi level opening the way for a half-metallic compensated ferrimagnet.

Heusler alloys containing Co and Mn are amongst the most heavily studied half-metallic ferromagnets for future applications in spintronics. Using state-of-the-art electronic structure calculations, we investigate the effect of doping and disorder on their electronic and magnetic properties. Small degrees of doping by substituting Fe or Cr for Mn scarcely affect the half-metallicity. A similar effect is also achieved by mixing the sublattices occupied by the Mn and sp atoms. Thus the half-metallicity is a robust property of these alloys.PACS numbers: 75.47. Np, 75.50.Cc, 75.30.Et The intensive development of electronics based on the combination of magnetic and semiconducting materials has brought in the center of scientific research new exotic materials. Half-metallic ferromagnets, which were first predicted by de Groot and collaborators in 1983, 1 have the peculiarity that the band-structure of the minorityspin electrons is semiconducting while of the majorityspin electrons is a normal metallic one. Such materials could maximize the efficiency of spintronic devices.2 Several Heusler compounds like NiMnSb and Co 2 MnSi have been predicted to be half-metals. 3Ishida and collaborators were, to the best of our knowledge, the first to study by means of ab-initio calculations the full-Heusler compounds of the type Co 2 MnZ, where Z stands for Si and Ge, and have shown that they are half-metals.4 Later the origin of half-metallicity in these compounds has been largely explained.3 Many experimental groups during the last years have worked on these compounds and have tried to synthesize them mainly in the form of thin films and incorporate them in spintronic devices. The group of Westerholt has extensively studied the properties of Co 2 MnGe films and they have incorporated this alloy in the case of spinvalves and multilayer structures.5 The group of Reiss managed to create magnetic tunnel junctions based on Co 2 MnSi.6 A similar study of Sakuraba and collaborators resulted in the fabrication of magnetic tunnel junctions using Co 2 MnSi as one magnetic electrode and Al-O as the barrier (Co 75 Fe 25 is the other magnetic electrode) and their results are consistent with the presence of half-metallicity for Co 2 MnSi.7 Dong and collaborators recently managed to inject spin-polarized current from Co 2 MnGe into a semiconducting structure.8 Finally Kallmayer et al. studied the effect of substituting Fe for Mn in Co 2 MnSi films and have shown that the experimental extracted magnetic spin moments are compatible with the half-metallicity for small degrees of doping.

Employing ab initio electronic structure calculations, we investigate the conditions for spin-gapless semiconducting (SGS) behavior in the inverse Mn 2 CoAl Heusler compound. We show that tetragonalization of the lattice, which can occur during films growth, keeps the SGS character of the perfect cubic compound. On the contrary, atomic swaps even between sites with different local symmetry destroy the SGS character giving rise to a half-metallic state. Furthermore, the occurrence of Co-surplus leads also to half-metallicity. Thus, we propose that in order to achieve SGS behavior during the growth of Mn 2 CoAl (and similar SGS Heusler compounds) thin films, one should minimize the occurrence of defects, while small deformations of the lattice, due to the lattice mismatch with the substrate, do not play a crucial role. V C 2014 AIP Publishing LLC.

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