Magnetism of Metals, Alloys and of Clusters of Transition Metal Atoms

A condition for local moment formation in metals derived by Stoddart and March (Ann. Phys. NY 1972 64, 174) is first used to discuss the ferromagnetism of body-centred-cubic Fe. A less detailed discussion is also added on Ni and Co. This leads into a treatment of the non- linear response of such 3d ferromagnets to dilute substitutional impurities. Antiferromagnets responding to local changes in the exchange field caused by such impurities are also studied, Mn in Cr being one such system discussed. The paper concludes with a brief summary of clusters of transition metal atoms, with most attention devoted to Cr and to Mn.

Screening-Dependent Study of Superconductivity in 3d-Transition Metals Binary Alloys Superconductors

In the present article, we report the screening-dependent study of the superconducting state parameters （SSPs）, viz. electron-phonon coupling strength A, Coulomb pseudopotential μ^＊, transition temperature TC, isotope effect exponent a, and effective interaction strength No V of 3d-band transition metals binary alloys superconductors have been made extensively in the present work using a model potential formalism and employing the pseudo-alloy-atom （PAA） model for the first time. Five local field correction functions proposed by Hartree （H）, Taylor （T）, Ichimaru-Utsumi （IU）, Farid et al. （F） and Sarkar et al. （S） are used in the present investigation to study the screening influence on the aforesaid properties. The present results of the SSPs obtained from H-screening are found in qualitative agreement with the available experimental data wherever exist.

Structure and Magnetic Properties of Fe1-xCx Solid Solution Prepared by Mechanical Alloying

Supersaturated solid solutions Fe1-xCx （0≤x≤0.9 ） of wide composition range have been prepared by mechanical alloying process. Nanocrystalline phase was formed for 0 ≤ x ≤ 0.67 and a large grain phase for 0.75 ≤ x ≤ 0.9. The large fraction of graphite volume puts off formation of nanocrystalline phase for high carbon content. In the large grain phase, magnetization follows simple magnetic dilution, and eoereivity He is mainly due to dissolution of carbon at grain boundaries. In the nanocrystalline phase the alloying effect of carbon is revealed by a distinct reduction of average magnetic moment. The increasing lattice constant with increasing carbon content is observed for x ≤ 0.5, suggesting that the high carbon concentration may enhance diffusion of carbon into the Fe lattice. It shows a discontinuity in the Hc variation with a grain size D of nanocrystalline phase. For small grain D below the critical value, Hc increases with D. For a large grain D, Hc decreases with increasing D. The solubility limit of carbon in a-Fe extended by nanocry- stalline phase formation is discussed.

Structural, elastic, phonon and electronic properties of a MnPd alloy

The structural, elastic, phonon and electronic properties of a MnPd alloy have been investigated using the first- principles calculation. The calculated lattice constants and electronic structure agree well with the experimental results. The microscopic mechanism of the diffusionless martensitic transition from the paramagnetic B2 （PM-B2） phase to the antiferromagnetic L10 （AFM-L10） phase through the intermediate paramagnetic L10 （PM-L10） phase has been explored theoretically. The obtained negative shear modulus C＇ - （C11 - C12）/2 of the PM-B2 phase is closely related to the instability of the cubic B2 phase with respect to the tetragonal distortions. The calculated phonon dispersions for the PM-L10 and AFM-L10 phases indicate that they are dynamically stable. However, the AFM-L10 phase is energetically most favorable according to the calculated total energy order, so the PM-L10 -＋AFM-L10 transition is caused by the magnetism rather than the electron-phonon interaction. Additionally, the AFM-L10 state is stabilized through the formation of a pseudo gap located at the Fermi level. The calculated results show that the CuAu-I type structure in the collinear antiferromagnetic state is dynamically and mechanically stable, thus is the low temperature phase.

In-situ fabrication of carbon compound NiFeMo-P anchored on nickel foam as bi-functional catalyst for boosting overall water splitting

The efficient non-noble metal-based bifunctional electrocatalyst for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)has attracted great interest,which is highly significant to enhance the efficiency of hydrogen production from water electrolysis.Herein,inspired by the appropriate hydrogen adsorption free energy of transition metal alloy and the strong corrosion resistance of phosphide in alkaline electrolyte,carbon compound NiFeMo-P anchored on nickel foam(NiFeMo-P-C)is obtained by simple one-pot hydrothermal and subsequent hydrogen reduction treatment.Remarkably,the NiFeMo-P-C exhibits excellent bifunctional electrocatalytic performances toward HER and OER with low overpotentials of 87 and 196 mV at 10 mA·cm^(-2),respectively.Moreover,the electrolyzer using NiFeMo-P-C as both cathode and anode only requires a cell voltage of 1.50 V to reach a current density of 10 mA·cm^(-2),along with an outstanding long-term stability for 50 h.The synergistic effect among alloys and phosphide,partially broken hollow morphology and porous nickel foam substrate jointly impart NiFeMo-P-C high electrocatalytic activity and superior durability.