2,233 research outputs found

    Influence of mixing the low-valent transition metal atoms (Y,Y^*=Cr,Mn,Fe) on the properties of the quaternary Co2_2[Y1x_{1-x}Yx^*_x]Z (Z=Al,Ga,Si,Ge,Sn) Heusler compounds

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    We complement our study on the doping and disorder in Co2_2MnZ compounds [I. Galanakis \textit{et al.}, Appl. Phys. Lett. \textbf{89}, 042502 (2006) and K. \"Ozdo\~gan \textit{et al.}, Phys. Rev. B \textbf{74}, (2006)] to cover also the quaterarny Co2_2[Y1x_{1-x}Yx^*_x]Z compounds with the lower-valent transition metals Y,Y^* being Cr, Mn or Fe and the sp atom Z being one of Al, Ga, Si, Ge, Sn. This study gives a global overview of the magnetic and electronic properties of these compounds since we vary both Y and Z elements. Our results suggest that for realistic applications the most appropriate compounds are the ones belonging to the families Co2_2[Mn1x_{1-x}Crx_x]Z with x>0.5x>0.5 irrespectively of the nature of the spsp atoms since they combine high values of majority DOS at the Fermi level due to the presence of Cr, and half-metallicity with large band-gaps. On the other hand the presence of Fe lowers considerably the majority density of states at the Fermi level and when combined with an element belonging to the Si-column, it even can destroy half-metallicity

    Effect of doping and disorder on the half-metallicity of full Heusler alloy

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    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

    Doping and disorder in the Co2_2MnAl and Co2_2MnGa half-metallic Heusler alloys

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    We expand our study on the full-Heusler compounds [I. Galanakis \textit{et al.}, Appl. Phys. Lett. \textbf{89}, 042502 (2006)] to cover also the case of doping and disorder in the case of Co2_2MnAl and Co2_2MnGa half-metallic Heusler alloys. These alloys present a region of very small minority density of states instead of a real gap. Electronic structure calculations reveal that doping with Fe and Cr in the case of Co2_2MnAl retains the half-metallicity contrary to the Co2_2MnGa compound. Cr impurities present an unusual behavior and the spin moment of the Cr impurity scales almost linearly with the concentration of Cr atoms contrary to the Co2_2MnZ (Z= Si, Ge, Sn) where it was almost constant. Half-metallicity is no more preserved for both Co2_2MnAl and Co2_2MnGa alloys when disorder occurs and there is either excess of Mn or spsp atoms

    Modeling toothpaste brand choice: An empirical comparison of artificial neural networks and multinomial probit model

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    Copyright @ 2010 Atlantis PressThe purpose of this study is to compare the performances of Artificial Neural Networks (ANN) and Multinomial Probit (MNP) approaches in modeling the choice decision within fast moving consumer goods sector. To do this, based on 2597 toothpaste purchases of a panel sample of 404 households, choice models are built and their performances are compared on the 861 purchases of a test sample of 135 households. Results show that ANN's predictions are better while MNP is useful in providing marketing insight

    Ab-initio design of half-metallic fully-compensated ferrimagnets: the case of Cr2_2MnZ (Z= P, As, Sb, Bi) compounds

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    Electronic structure calculations from first-principles are employed to design some new half-metallic fully-compensated ferrimagnets (or as they are widely known half-metallic antiferromagnets) susceptible of finding applications in spintronics. Cr2_2MnZ (Z= P, As, Sb, Bi) compounds have 24 valence electrons per unit cell and calculations show that their total spin moment is approximately zero for a wide range of lattice constants in agreement with the Slater-Pauling behavior for ideal half-metals. Simultaneously, the spin magnetic moments of Cr and Mn atoms are antiparallel and the compounds are ferrimagnets. Mean-field approximation is employed to estimate their Curie temperature, which exceeds room temperature for the alloy with Sb. Our findings suggest that Cr2_2MnSb is the compound of choice for further experimental investigations. Contrary to the alloys mentioned above half-metallic antiferromagnetism is unstable in the case of the Cr2_2FeZ (Z= Si, Ge, Sn) alloys

    Defects in CrAs and related compounds: a route to half-metallic ferrimagnetism

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    Half-metallic ferrimagnetism is crucial for spintronic applications with respect to ferromagnets due to the lower stray fields created by these materials. Studying the effect of defects in CrAs and related transition-metal chalcogenides and pnictides crystallizing in the zinc-blende structure, we reveal that the excess of the transition-metal atoms leads to half-metallic ferrimagnetism. The surplus of these atoms are antiferromagnetically coupled to the transition-metal atoms sitting at the perfect lattice sites. The needed condition to achieve half-metallic ferrimagnetism is to prevent the migration of the spsp atoms to other sites and the atomic swaps

    Ferrimagnetism and antiferromagnetism in half-metallic Heusler alloys

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    Half-metallic Heusler alloys are among the most promising materials for future applications in spintronic devices. Although most Heusler alloys are ferromagnets, ferrimagnetic or antiferromagnetic (also called fully-compensated ferrimagnetic) alloys would be more desirable for applications due to the lower external fields. Ferrimagnetism can be either found in perfect Heusler compounds or achieved through the creation of defects in ferromagnetic Heusler alloys.Comment: To be considered for the proceedings of the International Conference on Nanoscale Magnetism (ICNM 07
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