Influence of mixing the low-valent transition metal atoms (Y, Y*=Cr, Mn, Fe) on the properties of the quaternary Co2[Y1−xYx*]Z (Z=Al, Ga, Si, Ge, or Sn) Heusler compounds

Abstract

We complement our study on the doping and disorder in Co2MnZ compounds [I. Galanakis et al., Appl. Phys. Lett. 89, 042502 (2006) and K. Özdogan et al., Phys. Rev. B 74, (2006)] to cover also the quaterarny Co2[Y1−xY *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[Mn1−xCrx]Z with x > 0.5 irrespectively of the nature of the sp 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.

Structural and magnetic properties of quaternary Co2Mn1-xCrxSi Heusler alloy thin films

“…As the Cr concentrations x increases above 0.6, secondary phases start to appear in L2 1 matrix and at x ¼ 1 the structure transforms to the disordered A2-type. Using ab initio calculations, Ö zdogan et al 18 have predicted that the L2 1 structure should remain stable in the Co 2 Mn 1-x Cr x Si with Cr substituting for Mn. They have shown that these intermediate quaternary compounds are half metals.…”

Magnetic properties of full-Heusler alloy Co2Fe1−xMnxAl films grown by molecular-beam epitaxy

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] These ferromagnets possess a gap at Fermi level in the minority spin band but exhibit metallic behavior in the majority spin band, thus leading to 100% spin polarization. Of these materials, Co-based fullHeusler alloys ͑Co 2 YZ͒ have attracted much more interest because of the half-metallic nature predicted theoretically and epitaxial growth easily on semiconductors.…”

“…Electronic structure calculations have revealed that doping with Fe in the case of Co 2 MnAl retained half-metallicity. 6,7 In spite of theoretical efforts for studying magnetic properties of Co 2 Fe 1−x Mn x Al, experimental investigation of their magnetic phases and magnetic anisotropies which depend on fabricating process is lacking. In this letter, we will present a detailed examination of the magnetic properties of epitaxial Co 2 Fe 1−x Mn x Al films grown on GaAs͑001͒ by molecular-beam epitaxy at different temperature T s and varying the Mn concentration x from 0 to 1.…”

“…Of these materials, Co-based fullHeusler alloys ͑Co 2 YZ͒ have attracted much more interest because of the half-metallic nature predicted theoretically and epitaxial growth easily on semiconductors. [5][6][7][8][9] Recently, some of these alloys including Co 2 MnSi, Co 2 FeAl, Co 2 MnAl, and Co 2 Cr 0.6 Fe 0.4 Al have been incorporated into magnetic tunnel junctions as ferromagnetic electrodes, achieving relatively high tunnel magnetoresistance. [10][11][12][13] It is suggested that these materials may play a key role for the technological development of spintronics.…”

Current-perpendicular-to-plane spin valves with a Co2Mn(Ga0.5Sn0.5) Heusler alloy

“…[20][21][22] Furthermore, the phase stability and the driving force for L2 1 ordering can be altered by adding quaternary element. 23,24 Recently, Varaprasad et al 25 reported that the bulk Co 2 Mn͑Ga 0.5 Sn 0.5 ͒ ͑CMGS͒ Heusler alloy exhibited a high current spin polarization of 72% at 4.2 K by the point contact Andreev reflection ͑PCAR͒ method, which is a relatively large value obtained for FM alloys by PCAR.…”