Magnetic properties of the non-stoichiometric TbCo2Nix alloys

The magnetic and magnetothermal properties of the non-stoichiometric TbCo2Nix (0 ≤ x ≤0.2) alloys were studied. It was found that the concentration dependence of the Curie temperature and magnetic moment of the 3d-sublattice have a maximum at x = 0.025. The obtained experimental magnetic properties of the TbCo2Nix alloys were discussed under assumption that the Co magnetic moment in the compounds changes with increasing x. The magnetic entropy change was determined using the temperature dependences of the magnetization and Maxwell's thermodynamic relation. The obtained results for TbCo2Nix were compared with those for the ErCo2Mnx alloys. © 2018 The Authors, published by EDP Sciences.The research was carried out within the state assignment of )$62 of 5Xssia (thePe ³0aJnet´ 1o ȺȺȺȺ-Ⱥ - 118020290129 -5) and supported by project of UB RAS (No. 18-10-2-5)

Unusual weak increase of Curie temperature and lattice parameters in Pr2Fe16.5Zr0.5

Crystal structure and magnetic and thermomagnetic properties of the Pr2Fe17-xMx compounds with M = Ti, V, Cr, Zr, Nb have been studied. The change of interatomic distances is not enough to explain the growth of the Curie point and it is necessary to assume the distribution of M = Ti, V, Cr, Nb atoms over the lattice positions, similar to that previously published for the Nd2Fe17-xMx compounds. It was established by neutron diffraction that Zr atoms substitute for Pr atoms in the 6c site and do not substitute for Fe atoms as might be expected from the original formula Pr2Fe16.5Zr0.5. So, the real composition of the substituted compound studied is Pr14.8(8)Zr0.52(8)Fe17. The magnetic moment of Fe atom and the magnetocaloric effect in the Pr2Fe17-xMx compounds decrease with decreasing Fe content. © Published under licence by IOP Publishing Ltd.Russian Foundation for Basic Research, RFBR: 18-02-00294The research was carried out within the state assignment of Minobrnauki of Russia (themes “Magnet” No. АААА-А18-118020290129-5, “Alloys” and “Flux” No. АААА-А18-118020190112-8) and supported in part by RFBR (project No. 18-02-00294)

Discovery of metastable tetragonal disordered phase upon phase transitions in the equiatomic nanostructured FePd alloy

Specific features of the phase transformation 1 → L10 (space groups Fm3m and P4/mmm, respectively) in single crystals of the equiatomic alloy FePd subjected to annealings both in the absence and in the presence of external uniaxial load, as well as in polycrystalline samples that had undergone severe plastic deformation via high-pressure torsion and subsequent annealing, have been studied. An investigation of the single crystals in a nanostructured state formed at different stages of ordering annealing was performed using optical polarization, thermomagnetic and transmission electron microscopy (TEM) methods. The nanostructured state of the polycrystalline samples FePd after deformation of both disordered and ordered FePd alloys and subsequent annealing was examined with the help of TEM and X-ray techniques. The results obtained were analyzed based on the known concepts of the symmetry theory of phase transitions. It was concluded that the atomic ordering in the FePd alloys is preceded by the formation of a ferroelastic disordered body-centered tetragonal phase with the structural type 6 and the space group I4/mmm. Experimental data that evidence the existence of a tetragonal disordered phase both in the single crystals and in the polycrystalline samples of FePd after severe plastic deformation and subsequent annealing are reported. Thus, the A1 ↔ A6 ↔ L10 phase transformation represents a combination of different types of phase transitions such as cooperative displacement A1 ↔ 6 and ordering A6 ↔ L10 of atoms

Effect of additions of zinc stearate on the properties of sintered Nd-Fe-B magnets

Zinc stearate additions have been used to increase the remanence of sintered Nd-Fe-B magnets produced by the powder metallurgy without powder pressing. Zinc stearate acts as an internal lubricant, i.e., it decreases the friction forces between the particles and favors an increase in the degree of texture of the powders, which is induced by the magnetic field. It is shown that the density and the magnetic hysteresis characteristics of sintered magnets produced using additions of 0.15 wt % zinc stearate exceeds the corresponding values obtained for magnets produced without this addition at a filling density of powders in containers of more than 2.9 and 3.0 g/cm3 in dry and wet states, respectively. Using additions of zinc stearate in the amount of 0.15% with respect to the weight of the powder, magnets with a density of 7.55 g/cm3, B r = 14.02 kG, H c = 7.91 kOe, and (BH)max = 46.1 MG Oe have been produced. © 2013 Pleiades Publishing, Ltd

Magnetic properties of the non-stoichiometric TbCo2Mn x and TbCo2Nix alloys

The crystal structure, magnetic and magnetothermal properties of non-stoichiometric TbCo2Mnx and TbCo2Nix alloys were studied. It was shown that single-phase compounds with the MgCu2-type structure exist up to a certain content of x (x < 0.4 for compounds with Mn and x ≤ 0.1 for compounds with Ni). The concentration changes of the lattice parameter, Curie temperature, magnetic moment of the 3d sublattice in TbCo2Mn x and TbCo2Nix alloys were compared. The magnetocaloric effect in alloys were estimated using data of magnetic and heat capacity measurements. © Published under licence by IOP Publishing Ltd.Russian Foundation for Basic Research, RFBR: 18-02-00294The research was carried out within the state assignment of Minobrnauki of Russia (theme “Magnet” No. АААА-А18-118020290129-5), supported in part by RFBR (project No. 18-02-00294)

Magnetic properties of the GdFeSi - GdTiSi solid solutions

The GdFe1-xTixSi, x=0-0.2 intermetallic compounds with a tetragonal crystal structure of the CeFeSi (P4/nmm)-type have been studied. It was obtained that the lattice parameter c and the Curie temperature increase quickly, whereas the lattice parameter a is almost unchanged in the system with increasing of Ti content. The GdFeSi compound is easily magnetized along the [001] axis, the field of magnetic anisotropy equals to ∼3.8 kOe at T = 90 K. The saturation magnetization does not change in the GdFe1-xTi x Si system. © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 18-72-10098Support by RSF (Project No. 18-72-10098) is acknowledged

Electrical resistivity, magnetism and electronic structure of the intermetallic 3d/4f Laves phase compounds ErNi2Mnx

The non-stoichiometric intermetallic compounds RENi2Mnx (RE = rare earth) with the cubic MgCu2-type structure display a large variety of magnetic properties which is due to a complex interplay between the degrees of freedom of the 3d and 4f electrons and their interactions. We performed a comprehensive study of the electrical resistivity, magnetic properties and the electronic structure of ErNi2Mnx (x =0, 0.25, 0.5, 0.75, 1, 1.25) compounds by employing a suitable set of complementary experimental approaches. We find an increase in electrical resistance compared to ErNi2 upon Mn doping, the residual resistivity ratio decreases with increasing manganese content. The Curie temperature exhibits a sharp increase to around 50 K for Mn concentrations x 0.5, whereas the saturation magnetization decreases with growing Mn content x 0.5. Valence band X-ray photoelectron spectroscopy reveals an increasing intensity of Mn 3d states near Fermi energy in dependence of Mn concentration and Curie temperature. Resonant photoelectron spectroscopy of ErNi2Mn0.75 reveals that the photoemission decay channels dominate the valence band spectra across the Er N5 and Mn L3 X-ray absorption maxima, whereas the L3VV Auger dictates the resonant valence band spectra close to and at the Ni L3 X-ray absorption edge

Effect of solid solution treatment and nitrogenation on magnetic properties of Sm2+αFe17Nx powders

The effect of solid solution treatment (SST) of Sm-Fe alloys and conditions of the nitrogenation on the structure and magnetic properties of the Sm2+αFe17Nx (α = 0 0.6) powders has been investigated. It is observed that the nitrided powders with the best hysteresis properties can be prepared from the Sm2.4Fe17 alloy after the SST at a temperature of 1050C (5 h) and heat treatment at 525C in a H2: N2 = 1: 1 gas mixture with a pressure of 2.5 atm. The additional ball milling of the powder enhances the coercivity to 6.4 kOe. © Published under licence by IOP Publishing Ltd.No.17-52-80072The work is supported by RFFI-BRICS project No.17-52-80072 and DST-BRICS under Proposal 258