We have carried out electronic structure and transport calculations for magnetic tunnel junctions (MTJ) composed of MgO and a half-metallic full Heusler alloy Co(2)MnSi on the basis of the density functional theory and the Landauer formula. We find that the density of states of Co atoms at the Co(2)MnSi/MgO(001) interface shifts toward the higher energy side due to the reduced symmetry, leading to a reduction of the spin polarization at the interface. Furthermore, we show that the majority-spin transmittance as a function of the in-plane wavevector [Formula: see text] has a broad peak centred at [Formula: see text] due to the tunnelling from the Δ(1) channel of Co(2)MnSi, while the transmittance from the Δ(5) channel is three orders of magnitude smaller than that of the Δ(1) channel. These results indicate that coherent tunnelling through the Δ(1) band is dominant also in an MTJ with Co(2)MnSi and an MgO barrier, like in Fe/MgO/Fe(001) MTJ and related systems.

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ABSTRACT:A chemoselective synthesis of poly(o-hydroxy-amide) as a polybenzoxazolc precursor has been developed. The polycondensation was carried out by addition of isophthaloyl dichloride to a solution of 3,3'-dihydroxybenzidine and lithium chloride in N-methylpyrrolidinone and gave the selective N-acylated polymer, poly(o-hydroxy-amide) with an inherent viscosity of0.7dLg-'-The structure of the polymer was characterized by IR, 1 H, and 13 C NMR spectroscopies. The model reaction was studied in detail to demonstrate the feasibility of the chemoselective polyamidation using benzoyl chloride and o-aminophenol. KEY WORDSChemoselective I Polyamidation I Poly(o-hydroxy-amide) I Isophthaloyl Dichloride I 3,3' -Dihydroxybenzidine I Photosensitive polyimides (PSPis) are widely used as protection and insulation layers of very large scale integrated circuit (VLSI), multi-chip modules for computers, telecommunications and thermal-heads because they simplify processing and do not need a photoresist used in the microlithography or a toxic etchant such as hydrazine.Most PSPis reported so far are a negative working type and need organic solvents as a developer. 1 -3 However, the negative PSPis tend to swell during development into the organic developer is an organic solvent, and it limits the pattern resolution. In order to overcome these problems, positive working PSPis that can be developed with water-based solutions have been attracting great interest. Although, several groups 4 -6 have reported resists consisting of poly(amic acid)s (PAAs) and o-diazonaphthoquinone (DNQ). However, dissolution rates of PAAs toward a 2.38% aqueous tetramethylammonium hydroxide (TMAH) solution are essentially too high to get sufficient dissolution contrast. Thus, the dissolution rates of PAAs have to be reduced by prebaking, or post exposure bake (PEB). Other DNQ sensitized approaches were made by introducing DNQ, and phenol moieties into PAA through sulfonic ester and ester linkages, respectively. 7 · 8 By controlling the contents of these groups to obtain good dissolution contrast, these PSPI-precursors have also been found to provide excellent positive images.Khanna et a/. 9 reported polyamides containing hydroxyl groups for a positive working DNQ sensitized photosensitive polymer system. Poly(o-hydroxy-amide) is a polybenzoxazole precursor, attracting increasing attention as an alkaline developable positive-type photosensitive polymer because of having an appropriate dissolution rate toward the 2.38% aqueous TMAH solution and no existence of phenol moiety after benzoxazole ring formation.Poly(o-hydroxy-amide)s are generally prepared by polycondensation of bis(o-aminophenol)s with diacid dichlorides in the presence of base. Acylation of oaminophenol might be expected to give either the Nor 0-acyl products. The lithographic performance of photosensitive polymer is profoundly affected by the existence of 0-acyl linkages. However, much attention has not been paid to the chemoselective polyamidation of bis(o-aminophenol)s. The present paper de...