Electronic structure of the ordered ferromagnetic alloys Ni3Mn,Ni3Fe,and Ni3Co

Calculations of the band structure of the ferromagnetic alloys Ni₃Mn, Ni₃Fe, and Ni₃Co are presented. The results are compared with experimental data. Change in the electronic structure as one goes from Ni₃Mn to Ni₃Co is analyzed. The occurrence of ferromagnetism in the alloys studied and the possibility of their existence in an ordered ferromagnetic state are examined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 82–88, June, 1988.     

Metallic magnetism in amorphous TM-Y (TM = Mn,Fe, Co,Ni) alloys

Systematic variations of magnetic properties in amorphous TM-Y (TM = Mn, Fe, Co, Ni) alloys are investigated on the basis of a finite temperature theory of amorphous metallic magnetism which takes into account both thermal spin fluctuations and the fluctuations due to structural and configurations disorder. It is shown that the magnetic phase diagrams calculated in the most random atomic configuration explain qualitatively the spinglass (SG) in Mn-Y, the SG ferromagnetism (F) transition in Fe-Y, and the F-paramagnetism transition in Co-Y and Ni-Y alloys. Magnetization vs concentration curves and susceptibility vs concentration curves as well as the effective Bohr magneton numbers are also shown to be explained qualitatively or semi-quantitatively by the theory. Their miscroscopic mechanisms are elucidated by means of their electronic structures, magnetic couplings, and atomic short range order. It is found that the magnetism in Fe-Y and Mn-Y amorphous alloys is strongly influenced by the atomic short range order. The result explains different magnetic phase diagrams in amorphous Fe-Y alloys and experimental SG transition temperatures in amorphous Mn-Y alloys.     

Hall effect in the ternary ordered alloys Ni3(Mn,Fe) and Ni3(Mn,Co) 1. Disordered solution solutions

The normal and anomalous Hall constants R₀ and R_s, respectively, and the resistivity have been measured for the quasibinary alloys Ni₃Mn-Ni₃Fe and Ni₃Mn-Ni₃Co. The results imply that in ternary alloys of Ni₃Mn containing slight Fe and Co impurities the hole regions of the Fermi surface make an important contribution to R₀ and that the primary scattering mechanism for the carriers corresponding to the anomalous Hall current in the alloys with Fe at room temperature is phonon scattering. It is concluded that the Fermi surface of the Ni₃Mn-Ni₃Fe alloys is closed.Translated from Izvestiya VUZ. Fizika, No. 3, pp. 21–29, March, 1970.     

Hall effect in the ternary ordered alloys Ni3(Mn,Fe) and Ni3(Mn,Co) II. Ordered solid solutions

An experimental study was made of the changes in the normal and anomalous Hall constants R₀ and R_s, respectively, the internal saturation induction B_s, and the resistivity ? during the ordering of quasibinary Ni₃Mn-Ni₃Fe and Ni₃Mn-Ni₃Co alloys. The concentration dependences of R₀, R_s, B_s, and ? were also studied in the ordered state of these alloys. It is concluded from an analysis of the experimental results that the decreases inR₀ and ? during the ordering of Ni₃Mn and as a result of the alloying of ordered Ni₃Mn with slight amounts (～5 at. %) of iron are due primarily to a decrease in the hole contribution to transport and to a decrease in the state density in the 3d band of these alloys near the Fermi level. The experimental data are in satisfactory agreement with the curve calculated by Yamashita et al. [6] for the density of 3d states in ordered Ni₃Mn and Ni₃Fe alloys.     

Penetration depths of superconducting U6X (X = Fe,Co, Mn)

The penetration depths, λ(T), of the heavy-fermion uranium-based superconductors U₆X (X = Fe, Co, Mn) have been measured as a function of temperature at ∼ 35 MHz. It was found that the temperature dependence of λ(T) for these compounds agrees well with the BCS theory. However, the values of λ(0) are large. By comparing the Slater-Pauling curve of the X elements with λ(0)^-1 for the U₆X superconductors, we have found that λ(0)^-1 is proportional to the saturation spin moments of elemental X, suggesting that there is a correlation between the superconductivity of these U₆X superconductors and the magnetic nature of the X elements.     

Simple explanation of tunneling spin-polarization of Fe,Co, Ni and its alloys

Values of the electron spin-polarization and their proportionality to bulk moments are easily explained by realizing that they are due to the itinerant d-like electrons. The proportionality of the tunneling current of superconductors and ferromagnets to the three-dimensional density-of-states is seen to occur naturally in the independent particle model. In contrast to tunneling, photoelectrons are dominated by localized electrons; these are also seen to be in agreement with calculated band structure.     

Quasiparticle dynamics in ferromagnetic compounds of the Co–Fe and Ni–Fe systems

We report a theoretical study of the quasiparticle lifetime and the quasiparticle mean free path caused by inelastic electron-electron scattering in ferromagnetic compounds of the Co–Fe and Ni–Fe systems. The study is based on spin-polarized calculations, which are performed within the G ⁰ W ⁰ approximation for equiatomic and Co(Ni)-rich compounds, as well as for their constituents. We mainly focus on the spin asymmetry of the quasiparticle properties, which leads to the spin-filtering effect experimentally observed in spin-dependent transport of hot electrons and holes in the systems under study. By comparing with available experimental data on the attenuation length, we estimate the contribution of the inelastic mean free path to this length.     

Magnetic contribution to the atomic volume of Co,Fe, Mn and Fe-3d metal alloys

The atomic volumes of the polymorphic 3d elements Mn, Fe and Co, and the average atomic volumes of alloys of Fe with Ni, Co, Mn, Cr and V are examined using a simple magnetovolume relation presented previously. The variation of the atomic volumes of the elements and of the alloys is shown to follow the variations in the magnetic moments associated with the atom through this relation.     

Investigation of the electronic characteristics of Ni3 (Fe,Ti) and Ni3 (Mn,Ti) alloys

The anomalous Hall (R_s) and the Nerst-Ettingshausen (Q_S) constants are measured for hardened Ni₃ (Fe, T_i) and Ni₃ (Mn, Ti) alloys. Scattering by phonons is detected, con tributing primarily to R_S as compared to scattering by magnetic inhomogeneities. Based on the positive signs of R_g and Q_S, it is concluded that 3d holes wi th antiparallel spin make the main contribution to the conductivity. A model is proposed for the electronic structure of the alloys studied.DeceasedTranslated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 59—63, June, 1981.     

First-principles study of LiMPO4 compounds (M=Mn,Fe, Co,Ni) as electrode material for lithium batteries

The intercalation voltages of cathode materials for rechargeable lithium-ion batteries are calculated for lithium-orthophosphate oxides LiMPO₄ (M=Mn, Fe, Co and Ni) using density-functional theory within the local-density (LDA) and LDA?+?U approximations. We show that the LDA?+?U approximation is able to reproduce the experimental volumes as well as the experimentally observed magnetic structures of the lithiated and non-lithiated compounds for which LDA qualitatively fail. Moreover, we find that, using the LDA?+?U approach, the experimental evolution of the lithium intercalation voltage along the series can be reproduced accurately.     

Interpretation of 3p-core-excitation spectra in Cr,Mn, Fe,Co, and Ni

Recent measurements of the 3p-core-excitation spectra of Cr, Mn, Fe, Co, and Ni are interpreted with an atomic model. The dispersion like line shape observed in these metals is attributed to the interference of 3p⁶3d^N → 3p⁵3d^N+1, which decays to 3p⁶3d^N?1?f via a super Coster-Kronig transition, with the direct excitation of 3p⁶3d^N → 3p⁶3d^N?1?f. The overall width of the line and some weaker features associated with it are related to the multiplet splittings of 3p⁵3d^N+1. The more symmetric line shape found for Cr, which is thought to be due to the absence of a large local moment, is explained in terms of the greater number of multiplets that contribute for a small moment ($\text{S=}\text{1}\text{2}$) as compared to a large moment ($\text{S=}\text{5}\text{2}$).     

Investigation of electronic configurations of Ni3(Fe,Ti) and Ni3(Mn,Ti) alloys

The ordinary Hall constant R_o of quenched Ni₃(Fe, Ti) and Ni₃(Mn, Ti) alloys was measured. The number of 4s and 3d electrons per atom was calculated on the basis of a four-band model. At low Ti concentrations in Ni₃(Fe, Ti) the contribution of 3d holes to R_o is negligible, but at high concentrations it is significant. The contribution of 3d holes to R_o for Ni₃(Mn, Ti) is considerable, and for Ni₃Mn and Ni₃(Mn +9.8% Ti) it is dominant. It is concluded that the changes in band energy of the bond between Ni and Ti in the considered systems are of a different nature.Deceased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 12–14, May, 1981.     

Calculation of the structure of the 4s band for Ni3Mn and Ni3Fe ordered alloys

Perturbation theory has been applied to the structure of the 4s band of Ni₃Mn and Ni₃Fe ordered alloys; the Fermi surfaces have been constructed for these alloys in the one-wave approximation, and the electron state densities and electron energy change on ordering have been calculated. It is found that the contribution of the 4s electrons to the ordering energy is much less than that of the 3d electrons.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 102–106, July, 1972.     

Electrical resistance of amorphous Fe−P,Co−P and Ni−P alloys

The electrical resistances of amorphous Fe–P, Co–P and Ni–P samples were measured as functions of temperatureT between 4 and 300 K in the as-prepared state and after annealing.We found that in the amorphous state the resistances of the iron and cobalt alloys increase proportional toT ² whereas the resistances of Ni–P samples vary essentially linearly with temperature. We attributed this result to the differences between the electronic structures of the materials under investigation.Below characteristic temperatures the resistances of all samples increase logarithmically with decreasing temperature. The logarithmic slope depends on composition and thermal treatment and is due to Kondo scattering.     

Chemical effect on the K shell fluorescence yield of Fe, Mn, Co, Cr and Cu compounds

Chemical effects on the K shell fluorescence yields of Fe, Mn, Co, Cr and Cu compounds were investigated. Samples were excited using 59.5 keV energy photons from a²⁴¹ Am radioisotope source. K X-rays emitted by samples were counted by a Si(Li) detector with a resolution 160 eV at 5.9 keV. Chemical effects on the K shell fluorescence yields (ωk) for Fe, Mn, Co, Cr and Cu compounds were observed. The values are compared with theoretical, semiempirical fit and experimental ones for the pure elements.     

Magnetocrystalline anisotropy of Ni and Mn substituted Nd2Fe14B compounds

Measurements of the effects of Ni and Mn substitutions for Fe on the magnetic properties of Nd₂Fe₁₄B compounds are reported. The Curie temperature is slightly increased with Ni substitution whilst in the case of replacement of Fe by Mn it is reduced drastically. A monotonic decrease of both the lattice parameters a and c is observed. The saturation magnetization is decreased by both Ni and especially Mn substitutions. The composition dependence of both the reorientation spin transition temperature and the cone angle has been measured. The influence of the 3d metal substitution on the Nd anisotropy has been measured and discussed. The composition dependence of the room temperature anisotropy field values, which is an important figure of merit for permanent magnet applications, decreases slightly in the case of Ni and drastically for Mn substitution. A comparison with the case of Co substitution has been made.     

Thickness-dependent magnetic properties of Ni81Fe19, Co90Fe10 and Ni65Fe15Co20 thin films

We present results of magnetization and magnetic anisotropy measurements in thin magnetic films of the alloys Ni₈₁Fe₁₉, Co₉₀Fe₁₀ and Ni₆₅Fe₁₅Co₂₀ that are commonly used in magnetoelectronic devices. The films were sandwiched between layers of Ta. At room temperature the critical thickness for all the films to become ferromagnetic is in the range 11–13 Å. In Co₉₀Fe₁₀ the coercivity and the anisotropy field both depend strongly on layer thickness.