N. V. Volkova

Phase Separation in Isostructural Systems between Ordering Alloy and Intermetallic Compound

The results of X-ray diffraction, Mossbauer effect and neutron diffraction studies and also magnetic, thermal and kinetic properties measurements of the ternary alloys PdMn x Fe 1-x are presented. It has been shown that the alloys in the 0.2 < x < 0.8 concentration range realize a micro-inhomogeneous state formed by isostructural phases of the constituent compositions: the ferromagnetic PdFe alloy undergoing atomic ordering and the antiferromagnetic PdMn intermetallic compound.

Magnetic properties of Ni3AlxMn1 − x alloys

Paramagnetic susceptibility of alloys Ni3AlxMn1 − x in the field of the transition between the ferromagnets described in the band theory (Ni3Al) and in the spin-localized (Ni3Mn) model of magnetic moments has been investigated. The concentration dependences of the paramagnetic Curie temperature, effective magnetic moment, and temperature-independent component of magnetic susceptibility have been determined.

Kinetic properties of ternary alloys Ni3MnxAl1 − x

Kinetic properties of Ni3MnxAl1 − x alloys have been studied at temperatures of 4.2 to 800 K in magnetic fields up to 12 MA/m. Separate contributions to the electrical resistance have been determined: the residual resistance, phonon component, and magnetic component. The behavior of the kinetic properties typical of the ferromagnets is observed, including the positive temperature coefficient of resistance and features in the form of a bend in the curves of the temperature dependence of resistance at the Curie temperature. It is shown that the parameters of the investigated kinetic properties change substantially upon the isomorphic concentration transition L12 → L12 from the ordinary superstructure of Ni3Mn type to the Ni3Al intermetallic compound. It has been revealed that the concentration dependence of the resistance can be described in terms of the percolation theory in the model of effective medium.

Transition from Itinerant Electron Magnetism to Localized Spin Magnetism in Ni3Al1-YMny Alloys

Magnetic properties of Ni3Al1-yMny alloys at y≤0.6 were investigated at T≤400 K in magnetic fields H≤4 MA/m. The concentration y dependencies of the spontaneous magnetic moment s, the effective magnetic moment eff, the Curie temperature ТС, the Weiss constant , and the temperature independent part of the magnetic susceptibility 0 were determined. The behavior of the Rhodes-Wohlfarth parameter р(y) in the transition region from the itinerant electron magnetism to the spin localized one is related to the increase in the spontaneous magnetic moment of Ni atoms inversely proportional to the average distance between Mn atoms with the highly localized magnetic moments.

Magnetic properties of Ni 3 Al x Mn 1 − x alloys

Paramagnetic susceptibility of alloys Ni3AlxMn1 − x in the field of the transition between the ferromagnets described in the band theory (Ni3Al) and in the spin-localized (Ni3Mn) model of magnetic moments has been investigated. The concentration dependences of the paramagnetic Curie temperature, effective magnetic moment, and temperature-independent component of magnetic susceptibility have been determined.

Magnetic properties of Ni3Al x Mn1 − x alloys

Paramagnetic susceptibility of alloys Ni3AlxMn1 − x in the field of the transition between the ferromagnets described in the band theory (Ni3Al) and in the spin-localized (Ni3Mn) model of magnetic moments has been investigated. The concentration dependences of the paramagnetic Curie temperature, effective magnetic moment, and temperature-independent component of magnetic susceptibility have been determined.

Local Spin Configurations of Fe Atoms in Microinhomogeneous PdMnxFe1-x Alloys

The Mössbauer spectra of PdMnxFe1-x alloys obtained at 80 K and at 300 K were studied in the 0.2 < x < 0.8 concentration range, in which there realizes a microinhomogeneous multiphase medium formed by isostructure phases of the constituent compositions: ferromagnetic PdFe (ТС=730 К) alloy undergoing atomic ordering and antiferromagnetic PdMn (TN=815 К) intermetallic compound. Magnetic properties studies evidence the presence of a third presumably noncollinear phase with its own ordering temperature lying below the Curie temperature of the ferromagnetic phase in the 0.2 < x < 0.8 concentration range. The Mössbauer spectra at 300 K exhibit a doublet for antiferromagnetic alloys (x > 0.8) and a sextet at Hhf ~350 kOe for ferromagnetic alloys (x < 0.2). In the intermediate concentration range several peaks 0 < Hhf < 350 kOe have been observed in the P(Hhf) curves, which result from microinhomogeneous multiphase state.

Magnetic structure and phase composition of microinhomogeneous PdMnxFe1 − x alloys

Mössbauer analysis of ternary PdMnxFe1 − x alloys in the range of concentrational transition from a ferromagnetic PdFe (F1) (TC = 725 K) to an antiferromagnetic PdMn (A) (TN = 815 K) phase has been carried out at temperatures T ∼ 80 and 295 K. An estimation of the relative volumes of the ferromagnetic and antiferromagnetic ordered phases in the molecular-field approximation was performed via calculation of the magnetic susceptibility of the alloy with x = 0.5; an analysis of the microstructure of the alloy with x = 0.45 was performed using the Bitter-figures technique. For the alloys with extreme concentrations, Mössbauer spectra have been obtained in two different forms, i.e., a doublet with Hhf < 50 kOe for the antiferromagnetic alloys with x > 0.8 and a sextet with Hhf ∼ 350 kOe for the ferromagnetic alloys with x < 0.2. In the intermediate concentration range, a wide spectrum of hyperfine fields 0 < Hhf < 350 kOe has been observed, which is due to a microinhomogeneous multiphase state.