Electronic structure, magnetic and optical properties of intermetallic compounds R2Fe17 (R=Pr,Gd)

In this paper we report comprehensive experimental and theoretical investigation of magnetic and electronic properties of the intermetallic compounds Pr2Fe17 and Gd2Fe17. For the first time electronic structure of these two systems was probed by optical measurements in the spectral range of 0.22-15 micrometers. On top of that charge carriers parameters (plasma frequency and relaxation frequency) and optical conductivity s(w) were determined. Self-consistent spin-resolved bandstructure calculations within the conventional LSDA+U method were performed. Theoretical interpetation of the experimental s(w) dispersions indicates transitions between 3d and 4p states of Fe ions to be the biggest ones. Qualitatively the line shape of the theoretical optical conductivity coincides well with our experimental data. Calculated by LSDA+U method magnetic moments per formula unit are found to be in good agreement with observed experimental values of saturation magnetization.Comment: 16 pages, 5 figures, 1 tabl

Competing anisotropy in the (TmxPr1-x)2Fe17 system

The magnetization curves of magnetically aligned finely powdered samples of the (TmxPr1-x)2Fe17 compounds have been measured at 4 K. The easy magnetization axis is oriented in the basal plane or along the hexagonal axis for the compounds with x = 0-0.3 and 0.7-1, respectively. This is because of the absence of magnetic ordering in the Tm and Pr subsystems in these ranges, respectively, and because of competing anisotropy of the subsystems. For the compositions with x = 0.4-0.6, both rare-earth subsystems are magnetically ordered and the easy magnetization axis is oriented between the basal plane and the hexagonal axis. The critical fields of FOMPs decrease quickly as the Pr or Tm content decreases in the ranges 0-0.3 and 0.7-1, respectively. The magnetization anisotropy also diminishes as the Tm content becomes smaller than x = 0.7. No influence of the intrinsic microdeformations on the magnetization of the compounds was detected. © 2018 The Authors, published by EDP Sciences

ESTIMATION OF MINERAL DENSITY OF BONE TISSUE GIRLS WITH VARIOUS LEVEL OF MOTOR ACTIVITY LIVING IN CONDITIONS OF KHMAO- YUGRA

In the presented study, the bone mineral density was assessed in girls with different levels of motor activity permanently living in the conditions of KhMAO-Ugra conditions. When comparing the data of densitometry, it was revealed that the girls engaged in martial arts had higher mineraliza-tion rates in the L2-L4 zone of the spine relative to girls with the usual level of motor activity. It is suggested that martial arts in the KhMAO-Ugra conditions can be used as an effective means of preventing structural and functional changes in bone tissue with female membersВ представленном исследовании была проведена оценка минеральной плотности костной ткани у девушек с разным уровнем дви-гательной активности, постоянно проживающих в условиях ХМАО-Югры. При сравнении данных денситометрии выявлено, что девушки, занимающиеся единоборствами, отличались более высокими по-казателями минерализации в зоне L2-L4 позвоночника относительно девушек с привычным уровнем двигательной активности. Сделано предположение, что занятия единоборствами в условиях ХМАО-Югры может быть использовано в качестве эффективного средства профилактики структурно-функциональных изменений костной ткани с лицами женского пол

A crystallographic phase transition within the magnetically ordered state of Ce_2Fe_17

X-ray diffraction experiments were performed on polycrystalline and single-crystal specimens of Ce$_{2}$Fe$_{17}$ at temperatures between 10 K and 300 K. Below $T_{\mathrm{t}}$ = 118$\pm$2 K, additional weak superstructure reflections were observed in the antiferromagnetically ordered state. The superstructure can be described by a doubling of the chemical unit cell along the $\mathbf{c}$ direction in hexagonal notation with the same space group $R \bar{3} m$ as the room-temperature structure. The additional antiferromagnetic satellite reflections observed in earlier neutron diffraction experiments can be conclusively related to the appearance of this superstructure.Comment: 8 pages, figures, submitted for publication in Phys. Rev.

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

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)

The Total Synthesis of Convolutamydine a in the Conditions of the Catalysis by β-Aminoalcohols of Pinane and Carane Structure

This work was supported by the Russian Foundation of Basic Research (grant № 15-03-09352 A)

STRUCTURAL AND MAGNETIC PHASE TRANSITIONS IN THE GdFeAl1-XSiX SYSTEM

GdFeAl1-xSix crystallizes into the phases: hexagonal of the MgZn2 (P63/mmc) type (x=0-0.8), tetragonal of the CeFeSi (P4/nmm) type (x=0.3-1) and cubic of the MgCu2 (Fd3m) type (x=0-0.7). Curie point increases for the hexagonal and cubic and decreases for the te-tragonal phases, moment Fe vanishes.Работа выполнена при поддержке проекта РНФ № 18-72-10098