I. V. Svechkarev

Conduction-electron-mediated exchange coupling in heavy rare earth metal compounds RM and RM3

Abstract The effect of pressure on the magnetic susceptibility of rare earth compounds GdM (MCu, Ag, Mg) and RIn 3 (RGd, Tb, Dy) has been investigated. The experimental data and results of ab initio calculations of the volume derivatives of the band structure and the exchange parameters for the corresponding series of compounds have been used to analayze the nature of the f-f interactions.

Electronic structure and magnetic properties of RNi5−xCux alloys (R=Y, La, Ce)

A study is made of the electronic structure and magnetic properties of RN5−xCux alloys (R=Y, La, Ce). The influence of substitution of nickel by copper on the features of the band structure and behavior of the magnetic susceptibility of these alloys is investigated. An analysis is made of the electronic states and interactions responsible for the magnetic properties of RNi5−xCux alloys.

de Haas–van Alphen effect in the diborides ScB2, ZrB2, and HfB2

ScB2, ZrB2, and HfB2 single crystals with hexagonal structure were grown and the properties of the Fermi surface of these compounds were studied using the de Haas–van Alphen effect (dHvA). The angular dependences of the frequencies of the dHvA oscillations in the planes (101¯0), (112¯0), and (0001) and the values of their effective cyclotron masses were measured. The frequencies of the oscillations found lie in the interval (0.96–28.2)×102T and the measured cyclotron masses lie in the range (0.09–0.87)m0. The values of the electron–phonon interaction constant λ on different sections of Fermi surface of ZrB2 were determined. The value of the constant λ ranges from 0.05–0.16.

Electronic structure and magnetic properties of GdM2 compounds

Electronic structure calculations are carried out for the ferromagnetic GdM2 compounds (M=Mg, Al, Fe, Co, Ni, Rh, Ir, Pt). By using the calculated susceptibilities, densities of electronic states, and exchange parameters, the Curie temperatures were evaluated for these compounds in the framework of a modified molecular-field approach. The calculated magnetic ordering temperatures appeared to be in improved agreement with experimental data, in contrast to the results obtained within a conventional mean-field theory.

Anisotropy of the magnetic properties and the electronic structure of transition-metal diborides

The temperature dependences of the magnetic susceptibility χ and its anisotropy Δχ=χ∥−χ⊥ have been measured for hexagonal single crystals of transition-metal diborides MB2 (M=Sc,Ti,V,Zr,Hf) in the temperature interval 4.2–300K. It is found that the anisotropy Δχ is weakly temperature-dependent, a nonmonotonic function of the filling of the hybridized p−d conduction band, and largest for group-IV transition metals. First-principles calculations of the electronic structure of diborides and the values of the paramagnetic contributions (spin and Van Vleck) to their susceptibility show that the behavior of the magnetic anisotropy is due to the competition between Van Vleck paramagnetism and orbital diamagnetism of the conduction electrons.

Features of the electronic spectrum and anomalous magnetism in the compounds YbPb3, YbSn3, CaPb3, and CaSn3

A theoretical study is made of the features of the band structure and magnetic susceptibility χ in the isovalent compounds YbP3, YbSn3, CaPb3, and CaSn3 with the AuCu3 lattice. It is shown that their anomalous, strongly temperature-dependent diamagnetism is due to the presence of points of degeneracy of the bands near the Fermi level. Analysis of the behavior of χ(T) gives refined values of the energies of the degeneracy points as precision reference marks in the band spectrum of these compounds.

Effect of pressure on magnetic properties of U(Ga1-xSnx)3 alloys

Abstract Magnetic susceptibilities, χ, of U(Ga1-xSnx)3 alloys (with x = 0 and 0.45) were studied under pressures up to 2 kbar in the temperature range 64–300 K. For UGa3 the pressure dependence of the Neel temperature was found to be dTN/dP = −1.1 ± 0.2 K/kbar. The obtained magnetovolume effect values, dlnχ/dlnV, and the results of detailed theoretical calculations of the electronic structure of UGa3 for different lattice parameters have been used to evaluate the volume dependence of the effective electron-electron interaction parameter.

Anomalous diamagnetism in aluminum-lithium alloys

In the region of the equilibrium solid solutions of lithium in aluminum an anomalous low-temperature peak of diamagnetism is observed which is due to the presence of a boundary point on a line of band degeneracy directly below the Fermi level. The position and structure of the peak in the average valence function are analogous to those studied previously in the aging systems Al–Mg and Al–Zn under suitable heat treatment. The value of the lithium impurity scattering parameter for the electron states in the vicinity of the point of degeneracy mentioned is estimated, and the linear relation of that parameter with impurity-related electrical resistance in aluminum alloys is established.

Pressure effect on the itinerant magnetism of MnSi and FeSi

Abstract The pressure effect on the magnetic susceptibility of MnSi and FeSi is studied in the temperature range 78–300 K. The obtained values of the magnetovolume effect in the paramagnetic phase of the monosilicides, and the results of detailed LMTO calculations of density of states at the Fermi level as a function of the lattice constant and temperature, were used to evaluate the volume derivatives of the electron-electron interaction parameter in MnSi and the energy gap in FeSi. The role of spin fluctuations in the magnetovolume effect is discussed.

Effect of pressure on magnetic properties of the fluctuating-valence system Ce(Ni1−xCux)5

The magnetic susceptibility χ of isostructural Ce(Ni1−xCux)5 alloys (0 ≤ x ≤ 0.9) is studied as a function of hydrostatic pressure up to 2 kbar for fixed temperatures of 77.3 and 300 K. The pronounced effect of pressure on the susceptibility is negative in sign and depends nonmonotonically on the Cu content, with a sharp maximum at x ∼ 0.4. The experimental results are discussed in terms of a valence instability of Ce ions in these alloys. The major contributions to χ and their volume dependences are calculated ab initio in a local spin density approximation for the reference compound CeNi5, and appear to be in close agreement with experimental data.