Mn2 CoSb compound: Structural, electronic, transport and magnetic properties

High-ordered Mn₂CoSb compound has been synthesized successfully by a melt-spinning technique. The band structure calculation shows that Mn₂CoSb is a true half-metallic ferromagnet characterized by an indirect Γ–X band gap of about 0.4007 eV around the Fermi level for minority-spin electrons. The calculated magnetic moment is per formula unit, which is close to the experimental value of . The electronic resistivity shows a power-law T^1.33 temperature dependence at low temperature. The T^1.5 dependence of the magnetization was observed at low temperature, which is expected from Bloch’s law.     

Opportunity of spinel ferrite materials in nonvolatile memory device applications based on their resistive switching performances

The opportunity of spinel ferrites in nonvolatile memory device applications has been demonstrated by the resistive switching performance characteristics of a Pt/NiFe(2)O(4)/Pt structure, such as low operating voltage, high device yield, long retention time (up to 10(5) s), and good endurance (up to 2.2 × 10(4) cycles). The dominant conduction mechanisms are Ohmic conduction in the low-resistance state and in the lower-voltage region of the high-resistance state and Schottky emission in the higher-voltage region of the high-resistance state. On the basis of measurements of the temperature dependence of the resistances and magnetic properties in different resistance states, we explain the physical mechanism of resistive switching of Pt/NiFe(2)O(4)/Pt devices using the model of formation and rupture of conducting filaments by considering the thermal effect of oxygen vacancies and changes in the valences of cations due to the redox effect.     

Comparative investigation of unipolar resistance switching effect of Pt/Mg0.6Zn0.4O/Pt devices with different electrode patterns for nonvolatile memory application

In this report, we study crystallization and Raman spectral and transmission electron microscopy (TEM) changes in amorphous and nanocrystalline Si. Micro-Raman spectra combined with TEM show that considerable crystallization occurs in a-Si:H and a-Si(Al) (the structure of aluminum-diffused amorphous Si/Al/c-Si), but no additional crystallization was observed for nc-Si:H, after the exposure to a laser or accelerating electrons. Meanwhile, moving toward lower or higher energy for a-Si:H and nc-Si:H, by contrast, the Raman shift appeared for a-Si(Al) as if it were for single-crystalline Si, in which it remained constant at one energy, as the laser intensity increased or decreased.     

Effect of the main-group elements on the electronic structures and magnetic properties of Heusler alloys Mn2NiZ (Z=In, Sn, Sb)

The magnetic properties and electronic structure of Mn₂NiZ (Z=In, Sn, Sb) have been studied. The magnetic structure of these alloys is mainly determined by the main-group element Z instead of the distance between the Mn atoms. Electronic structure calculations suggest that Mn₂NiIn and Mn₂NiSn are both ferrimagnets with antiparallel alignment between the Mn moments. But this antiferromagnetic coupling is weakened by the increasing number of valence electrons of the Z atoms. When it comes to Mn₂NiSb, a ferromagnetic coupling between the Mn atoms is observed. Mn₂NiSn and Mn₂NiSb have been synthesized successfully. Their M_s at 5 K agree well with the theoretical value.     

The β-nucleated ternary composites of polypropylene/nano-CaCO3/short poly(ethylene-terephthalate) fiber

A serial of β-nucleated polypropylene (β-PP)/nano-calcium carbonate (nano-CaCO₃)/ short poly(ethylene-terephthalate) (PET) fiber composites were prepared using extrusion blending. Maleic anhydride grafted PP (PP-g-MA) was used to modify the compatibility. The relationships among components, structure, and properties of the PP composites were studied. The results show that adding nano-CaCO₃ improved the mechanical properties of the materials. Adding PET fiber increased the rigidity and toughness but the tensile strength decreased. PP-g-MA modified the compatibility of the components of the composites. Both PET fiber and nano-CaCO₃ had nucleation effect on the PP crystallization and slightly induced the formation of β crystals. Ternary β-PP/nano-CaCO₃/PET fiber composites contained high β-crystal content, and the compatibilizer exhibited synergy effect with β nucleating agent to further increase the β-crystal content in the blends. Mo’s method could satisfactorily describe the nonisothermal crystallization behavior of ternary composites, whereas Jeziorny and Ozawa methods failed to do the same ideally.     

Effect of Cr on the electronic structure of Co3Al intermetallic compound: A first-principles study

The effect of doping with Cr on the electronic structure and magnetism of Co₃Al has been studied by density functional calculations. It has been found that the Cr atom has a strong site preference for the B-site in Co₃Al. With the substitution of Cr for Co, the total densities of states (DOS) change obviously: A DOS peak appears at E_F in the majority spin states and an energy gap is opened in the minority spin states. The effect of Cr in Co₃Al is mainly to push the antibonding peak of the Co (A,C) atoms high on the energy scale and to form the energy gap around E_F, and also to contribute to the large DOS peak at E_F in the majority spin direction. The calculations indicate a ferromagnetic alignment between the Co and Cr spin moments. The calculated total magnetic moment decreases and becomes closer to the Slater–Pauling curve with increasing Cr content. This is mainly due to the decrease of the Co (A,C) spin moments. At the same time, the moments of Co (B) and Cr (B) only change slightly.     

高度非对称二元系超额焓的简化计算

焓超额焓是化学工业中混合与分离过程的重要热力学性质。由于超额焓的实验测定比较困难且不具有连续性;因此,国内外都对混合物超额焓的理论计算进行了大量的研究。同时,状态方程法在混合物超额焓的计算中也得到日益广泛的研究。计算体系也从常压体系扩展到高压体系以及...