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Confined in the extended solid with a widespread K2NiF4 structure type, cation Dy3+ exhibits magnetic bistability under a zero field.

The first instance of a rare-earth single-ion magnet in a robust extended solid has been found, which possesses a crystal structure different from apatite. The compound exhibits slow relaxation of magnetization in a zero field revealing simultaneously two energy barriers for magnetization reversal.

Tb-diluted and Tb-rich apatite-type silicates with compositions Y7.75Tb0.25Ca2(SiO4)6O2 and Tb8Ca2(SiO4)6O2, respectively, exhibit field induced multiple slow relaxation of magnetization. The former reveals two slow relaxation paths, the latter only one with a longer relaxation time of several seconds. The relaxation features of the Tb-diluted one are comparable with those of analogue compounds, where Tb is replaced by Dy, as well as with those of a Tb-doped calcium phosphate apatite. The relaxation parameters of the Tb-rich compound virtually match those of the Dy-based analogue Dy8Ca2(SiO4)6O2. The latter represents the first instance of independence of magnetization relaxation on the nature of a paramagnetic rare-earth metal ion in single ion magnet like materials.

Tb-diluted and Tb-rich apatite-type silicates with compositions Y

The influence of Ag+ ions and Mn non-stoichiometry on the magnetic properties and magnetocaloric effect in the La0.9–xAgxMn1.1O3 compounds has been studied. The Ag+ ions content substituting for trivalent lanthanum ions was varied from x = 0.05 to 0.3. Magnetic measurements have been performed over a wide temperature (350–5 K) and magnetic field (up to 5 T) ranges. All the manganites studied show the ferromagnetic-like ordering with a first order magnetic phase transition. The magnetic entropy changes were evaluated from the isothermal curves of magnetization versus an applied magnetic field using both the thermodynamic Maxwell relation (MR) and calculation based on the Landau theory of phase transitions. The largest values of the magnetocaloric effect as well as the relative cooling power among the studied manganites are equal to 5.76 J/(kg K) and 185 J/kg, respectively, for La0.7Ag0.2Mn1.1O3 in the magnetic field change of 5 T near the Curie temperature of TC = 271 K. A good correlation between the magn...

The article presents the results of studies of the influence of the cutting path length on the change in the microgeometry of the circular saw tooth. The factor — the length of the cutter path in the material — varied from 120 m to 4 km. The material to be processed is a laminated particle board of the brand П-А 19 mm thick. The experiments were carried out on the saw experimental installation. The installation has the ability to adjust the speed of rotation of the saw and the feed rate of the material. A disk with wedge-shaped slots was used as a cutting tool. The test tooth was made of a hard alloy VK6M grade in the slot. The front angle of the tooth was 11 °, the posterior angle was 15 °, and the taper angle was 64 °. After working on a given distance, it was removed from the body of the saw, examined and photographed on a large instrumentation microscope MBI-2. Estimated wear of the tooth surface by measuring the distance from the top of the tooth to the tangent to the contour of the saw tooth, carried out at specified angles. A set of consecutive tangent lines to the smooth convex contour of a worn surface, (or lines, if, consider the section) allows replacing the continuous profile line with straight line segments. Measurements were carried out in a tooth cross-section perpendicular to the short cutting edge. Identified specific values of wear of the saw tooth, depending on the length of the cutting path. It is shown that with an increase in the length of the cutting path, the wear on the rear face significantly exceeds this parameter from the front face. The distribution of wear in the directions from the front to the rear shows that they are very well approximated by a second-order curve (this is indicated by a correlation coefficient close to unity). From this it follows that the nature of wear with an increase in the cutting path does not change. The point separating the front and rear faces is defined. Identified the drift of this point, depending on the growth of wear. Localization of the top of the parabola with an increase in the cutting path is shifted towards the front face. The displacement is insignificant, however, it shows the tendency of the apex to drift towards the front face. Physically, the top of a parabola characterizes the location of the blade on the surface of a blunt tooth.

The NiMn0.95Ti0.05MnGe and Ni1–xTixMnGe (x = 0.05, 0.15 and 0.25) compounds have been studied by X-ray (at room temperature), neutron diffraction (2–360 K), DSC (130–390 K) and magnetic studies (2–...

Structural properties, magnetization and magnetocaloric effect measurements in the compounds based on lanthanum–strontium–bismuth manganites La 0.7 Sr 0.3 − x Bi x MnO 3 (LSBiMO) with 0.05 ⩽ x ⩽ 0.30 have been performed. The valence states of elements entering into the composition of investigated LSBiMO samples were analyzed for x = 0.15 and 0.3 using the HR XPS spectra of Bi 4f, La 3d, Mn 3s and Sr 3d. According to X-ray powder diffraction data the crystalline structure of the samples is perovskite-like with a small rhombohedral distortion. The a and c lattice parameters and unit cell volume V are established to increase with increasing Bi content. All the manganites show ferromagnetic-like ordering with second order phase transition to paramagnetic state. The Curie temperature and magnetization decrease at substitution of Sr 2+ for Bi 3+ ions. The magnetic entropy changes were calculated using the field dependence of isothermal magnetization in the terms of the thermodynamic Maxwell relation. The maximum magnetic entropy change value was shown to be 0.94 J kg −1 K −1 for x = 0.05 for a field change of 1 T.

The Mn2−xFexP0.5As0.5 compounds (x = 0.7 and 1.0) studied exhibit the magnetic phase transitions, which are accompanied by a magnetic entropy change. For x = 1 the PM–FM transition is of the first order one with a weak (2–3 K) thermal hysteresis in the vicinity of TC = 275 K. The Mn1.3Fe0.7P0.5As0.5 compound possesses two magnetic transitions: the second-order PM–FM transition at TC = 190 K, followed by the FM–AFM transition at TN = 90 K, leading to normal and inverse magnetocaloric effects, respectively. The maximum values of magnetic entropy change are equal to 17 J kg−1 K−1 in MnFeP0.5As0.5 and 5 J kg−1 K−1 in Mn1.3Fe0.7P0.5As0.5 for a field change of 5 T. The magnetic entropy changes were calculated using both the isofield magnetization curves versus temperature and the isothermal magnetization curves versus applied magnetic field. The magnetocaloric effect in MnFeAs0.5P0.5 is discussed in the terms of both the thermodynamic Maxwell relation and the Clausius–Clapeyron equation.

Magnetic and Ferroelectric Ordering in the TbMnO3 Film A. Sazanovicha,∗, Yu. Nikolaenko, W. Paszkowicz, V. Mikhaylov, K. Dyakonov, Yu. Medvedev, V. Nizhankovskii, V. Dyakonov and H. Szymczak Institute of Physics, PAS, al. Lotnikow 32/46, 02-668 Warsaw, Poland A.A. Galkin Donetsk Physico-Technical Institute, NANU, 83114 Donetsk, R. Luxembourg str. 72, Ukraine A.F. Io e Physico-Technical Institute RAN, Politekhnicheskaja 26, 194021 St.-Petersburg, Russia International Laboratory of High Magnetic Fields and Low Temperatures, 53-421 Wrocaaw, Poland

In this work, the influence of linear deformation on the magnetic resonance spectrum including the surface spin wave mode in La 0.67 Ca 0.33 MnO 3 manganite film grown on LiNbO 3 substrate has been investigated using a microwave technique. The parameters of the spectrum are established to depend strongly on strains in the film that influence both the profile of the magnetic resonance spectrum and the mode position and intensity. The magnetostriction constants of both the bulk film and surface mode were first determined using the shift of resonance fields as a function of mechanical stress. The tensile strain is shown to favor excitation of the surface spin-wave mode, and its influence is stronger on the film surface layer.

The effect of particle size on the magnetic properties of RMnO3 (R = Pr, Nd, and Tb) has been investigated by magnetometric and X-ray and neutron diffraction methods. The samples were obtained by a sol–gel method. The investigated compounds with a grain size < 100 nm crystallize in the orthorhombic crystal structure described by the Pnma space group. The crystal parameters for the nanoparticle compounds are slightly smaller than those for bulk materials Low temperature magnetic and neutron diffraction data indicate the difference in their magnetic properties. For the nanoparticle PrMnO3 (annealed at 900 °C) and NdMnO3 samples, the magnetic ordering of CxFy-type exists in Mn sublattice while in PrMnO3 annealed at 800 °C it is missing. The Nd moments order below T ≈ 13 K according to a ferromagnetic arrangement of Fy-type.

The pressure, magnetic-field, and excess manganese effects on transport and magnetoresistance effect (MRE) are studied in both epitaxial films and bulk ceramics of the manganites (La0.7Ca0.3)1−xMn1+xO3−y (x=0–0.2). A comparison of the electrical behavior in both kinds of samples of similar composition at hydrostatic pressures of up to 1.8GPa and in magnetic fields of up to 8kOe is performed. The pressure and magnetic-field effects are shown to increase with increasing manganese content. Experimental data show that the effects of pressure and magnetic field on the temperatures of both the metal-insulator transition (TMD) and the MRE peak (TMR) are considerably stronger in the films than in the ceramics. The hydrostatic pressure increases TMD and TMR. It was shown that for both types of samples the magnetoresistance effect is affected in opposite ways by pressure and magnetic field. A direct correlation is established between TMD and conductivity bandwidth as well as between MRE and concentration of charge ...

Recently an anomalous acoustoelectrical (AE) effect produced by surface acoustic waves (SAW) in thin La0.67Ca0.33MnO3 films deposited on a piezoelectric LiNbO3 substrate was discovered [Phys. Rev. Lett. 87 (2001) 146602]. The SAW, launched along the distinct crystallographic axis (+z) of the structure, induces a dc current IAE in the film, which in the ordinary AE effect would be odd with respect to the SAW wave vector q . However, in the investigated case IAE contains, along with the ordinary odd component, an anomalous one, which is even in q . The anomalous effect dominates near the metal–insulator transition, while the ordinary effect prevails at high and low temperatures. The anomalous effect appears to depend on strong modulation of the film conductivity resulting from the elastic deformations carried by the SAW. We have investigated the influence of an in-plane magnetic field H on the magnitude of IAE, and found an increase of about 50% when H was parallel to q . The increase was limited to the anomalous component of IAE. We speculate that this may be caused by magnetic field induced changes in the conductivity dependence on pressure. The ordinary AE current was left essentially unchanged. Apparently the boost given to this component by the increase of conductivity in a magnetic field is compensated by the corresponding SAW attenuation decrease. We have also conducted IAE measurements with the SAW split into two components of equal amplitude, propagating in the film in opposite directions. As a result, we have obtained cancellation of the ordinary IAE component and augmentation of the anomalous one, i.e. we have confirmed our understanding of the AE effects.

Measurements of ferromagnetic resonance (FMR) in both in-plane (H‖) and out-of-plane (H⊥) magnetic field configurations have been performed on a series of epitaxial (La0.7Ca0.3)1−xMn1+xO3 films. The FMR linewidths have a local maximum near the Curie point and increase continuously at low temperatures. The effective anisotropy of the films has the easy-plane character. The angular dependences of Hres were found to be in reasonable agreement with the theoretical ones, taking into account the second- and fourth-order terms of the magnetic anisotropy energy. A reasonable agreement between ΔHres(α) and Bloch type dissipation was obtained only for deviations of the external field from the normal to the film plane up to α=20°. From the temperature and angular dependences of the FMR spectra, the main magnetic parameters such as the effective magnetization, effective field Heff, anisotropy field HA2, and FMR linewidth were estimated.

The spin-wave resonance (SWR) spectra have been observed in the (001) oriented La 0.7 Mn 1.3 O 3− δ epitaxial films. The spectra consist of a series of well-resolved spin-wave modes clearly seen in the perpendicular external field configuration. It is shown that the spins are completely pinned on both sides of the film surface. Based on a study of the SWR spectra the value of the spin-wave exchange constant, D , is found to be 150 meV A 2 . This value of D correlates well with this one determined for all known until now manganites.

Moscow has a large population of immigrants and migrants from across the Former Soviet Union. Little is studied about men who have sex with men (MSM) within these groups. Qualitative research methods were used to explore identities, practices, and factors affecting HIV prevention and risks among immigrant/migrant MSM in Moscow. Nine interviews and three focus group discussions were conducted between April-June 2010 with immigrant/migrant MSM, analyzed as a subset of a larger population of MSM who participated in qualitative research (n=121). Participants were purposively selected men who reported same sex practices (last 12 months). Migrants were men residing in Moscow but from other Russian regions and immigrants from countries outside of Russia. A socioecological framework was used to describe distal to proximal factors that influenced risks for HIV acquisition. MSM ranged from heterosexual to gay-identified. Stigma and violence related to homophobia in homelands and concerns about xenophobia and distrust of migrants in Moscow were emerged as key themes. Participants reported greater sexual freedom in Moscow but feared relatives in homelands would learn of behaviors in Moscow, often avoiding members of their own ethnicity in Moscow. Internalized homophobia was prevalent and linked to traditional sexual views. Sexual risks included sex work, high numbers of partners, and inconsistent condom use. Avoidance of HIV testing or purchasing false results was related to reporting requirements in Russia, which may bar entry or expel those testing positive. HIV prevention for MSM should consider immigrant/migrant populations, the range of sexual identities, and risk factors among these men. The willingness of some men to socialize with immigrants/migrants of other countries may provide opportunities for peer-based prevention approaches. Immigrants/migrants comprised important proportions of the MSM population, yet are rarely acknowledged in research. Understanding their risks and how to reach them may improve the overall impact of prevention for MSM and adults in Russia.

X-ray diffraction and magnetic using dc and ac methods measurements of the polycrystalline and nanosize REMnO3 (RE = Pr, Nd) powdered samples have been performed. The nanosize manganites were synthesized with a sol-gel method at different (800, 850 and 900 °C) temperatures. The average size of synthesized nanoparticles (from 56 to 89 nm) and polycrystalline powders (above 200 nm) was estimated using the x-ray diffraction data. All the compounds studied crystallize in the orthorhombic crystal structure (space group Pnma) at room temperature with smaller values of the lattice parameters in the nanosamples. The temperature-dependent ac magnetic susceptibilities show a sharp high-temperature peak connected with Mn magnetic moments ordering. The low-temperature maximum of magnetic susceptibility is proposed to be due to the polarization of the rare-earth sublattice by an effective exchange field of the Mn ordered sublattice. The antiferromagnetic ordering of Mn sublattice and paramagnetic Curie temperatures as well as the magnetic moment values for the nanosize samples was found to be smaller than those for polycrystalline sample.

We report on acoustic and acoustoelectric (AE) studies of La 0.67 Ca 0.33 MnO 3 (LCMO) films deposited on a LiNbO 3 substrate. Surface acoustic wave (SAW) attenuation in the LCMO films has been measured at different sound frequencies in the wide temperature range. Our measurements confirm the hole-like conductivity in La 0.67 Ca 0.33 MnO 3 films and reveal an anomalous (even in the SAW wave vector) contribution to the AE effect, which coexists with the ordinary (odd) effect. The anomalous AE effect is shown to be due to a strong modulation of the film conductivity produced by elastic deformations carried by the SAW.

X-ray, neutron powder diffraction (NPD), and magnetic measurements were performed in order to investigate the effect of Pr substitution for La on crystallographic structure, on character of magnetic ordering, and on transition temperature in ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Pr}}_{x}\mathrm{Mn}{\mathrm{O}}_{3+\ensuremath{\delta}}$ manganites series $(0\ensuremath{\leqslant}x\ensuremath{\leqslant}1.0)$. Strong dependence of structural and magnetic properties on average $A$-site ionic radius was found. The magnetic phase diagram, characterizing Pr concentration dependence of the phase transition temperature, was constructed, based on magnetic and on NPD results. In the compounds with $xl0.7$, the ferromagneticlike behavior with ferromagnetic moment aligned along the $b$ axis was observed in the temperature interval below the Curie temperature, ${T}_{\mathrm{C}}$, varying in the range of $113--153\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, down to Mn ions canted spin arrangement transition temperature, ${T}_{\mathrm{CANT}}$, varying in the range of $73--115\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. It was found that ${T}_{\mathrm{C}}$ changes nonmonotonously with Pr content, it decreases rapidly for $xl0.3$ and for $xg0.6$, while is practically independent on $x$ for $0.3lxl0.6$. The Mn magnetic moments increase from 3.2 for $x=0$ to 3.6 for $x=0.3$ before decreasing to $1.7\phantom{\rule{0.3em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}∕\mathrm{Mn}$ for $x=1.0$ and form a canting structure with canting angle decreasing from 32\ifmmode^\circ\else\textdegree\fi{} for $x=0$ to 16\ifmmode^\circ\else\textdegree\fi{} for $x=0.3$ and then increasing to 70\ifmmode^\circ\else\textdegree\fi{} for $x=1.0$. The NPD and x-ray diffraction data indicate that Pr doping in $\mathrm{La}\mathrm{Mn}{\mathrm{O}}_{3}$ is accompanied by changes of both the lattice parameters and crystal structure. The compound with $x=0$ was shown to have a rhombohedral crystal structure, while the samples with $0.1\ensuremath{\leqslant}x\ensuremath{\leqslant}0.6$ have orthorhombic symmetry with a small Jahn-Teller distortion (or pseudocubic) which continuously transforms towards highly distorted orthorhombic structure for $xg0.6$. From ac magnetic susceptibility, studied under hydrostatic pressure up to $1.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, it was found that ${T}_{\mathrm{C}}$ and ${T}_{\mathrm{CANT}}$ change linearly with an applied pressure. The results are interpreted taking into account the competition of ferromagnetic double-exchange and antiferromagnetic superexchange interactions. This competition leads to a low temperature disordered system with spin canted features as a result of a decrease of the average $A$-site cation radius followed by decrease of Mn-O bond lengths, Mn-O-Mn bond angles, and the static Jahn-Teller distortion of the $\mathrm{Mn}{\mathrm{O}}_{6}$ octahedra.

We have studied the acoustoelectric (AE) effect produced by surface acoustic waves (SAW) in a monolithic layered structure, composed of a piezodielectric LiNbO3 substrate and a La0.67Ca0.33MnO3 film. The experiments unexpectedly revealed in the longitudinal AE effect an anomalous contribution, invariant upon reversal of SAW propagation, which coexists with the ordinary (odd in wave vector) effect. The anomalous effect dominates near the metal-insulator transition, while the ordinary effect prevails at high and low temperatures. We show that the anomalous effect is caused by strong modulation of the film conductivity produced by the SAW elastic deformations.

We have studied the acoustoelectric (AE) effect produced by surface acoustic waves (SAW) in a monolithic layered structure, composed of a piezodielectric LiNbO3 substrate and a La0.67Ca0.33MnO3 film. The experiments unexpectedly revealed in the longitudinal AE effect an anomalous contribution, invariant upon reversal of SAW propagation, which coexists with the ordinary (odd in wave vector) effect. The anomalous effect dominates near the metal-insulator transition, while the ordinary effect prevails at high and low temperatures. We show that the anomalous effect is caused by strong modulation of the film conductivity produced by the SAW elastic deformations.

Complex drainage of land comprises engineering, biological, chemical, economic and organizational systems to improve the human environment and, especially, increase the fertility of land. The latter includes fields planning, liming, applications of mineral and organic fertilizers, primary sowing to grass, and other environmental arrangements.

X-ray diffraction and magnetic measurements of polycrystalline and nanosize TbMnO3 manganites were performed. All the compounds studied crystallize in the orthorhombic crystal structure (space group Pnma) at room temperature. Nanosize manganites were synthesized via the sol-gel method at different (800 and 900 °C) temperatures. The average size of the synthesized nanoparticles (from 45 to 70 nm) was estimated by x-ray diffraction and low-temperature adsorption of argon. Information about the evolution of properties of TbMnO3 with changing grain size, temperature, and magnetic field was obtained. Crystal structure parameters of nano-samples change slightly with changing nanoparticle size. Peculiarities of magnetic ordering in polycrystalline and nanosize TbMnO3 were compared. Magnetization and the Neel temperature corresponding to antiferromagnetic ordering of the Tb3+ sublattice decrease as the particle size is reduced. Inverse magnetic susceptibility of the nanoparticle samples deviates from the Curie–Weiss law below 50 K; this is related to the magnetic ordering of Mn3+ moments. Some peculiar anomalities related to the magnetic ordering of Tb3+ and Mn3+ sublattices were noticed in specific heat values of the nanosize samples.

In this paper, the crystallographic, magnetic, thermomagnetic, and magnetocaloric properties of the quenched NiMn1−xCrxGe (x = 0.04, 0.18, and 0.25) half-Heusler alloys have been studied by x-ray diffraction, differential scanning calorimetry and magnetization measurements. An influence of partial substitution of Cr for Mn and quenching of the samples on the character of structural and magnetic phase transitions is presented. Quenching of the alloys results in the formation of two phase (orthorhombic and hexagonal) crystal structure. The magnetic properties were investigated by means of magnetization measurements over a wide temperature (5–400 K) and magnetic field (up to 60 kOe) ranges. The experimental data indicate that at quenching and with increasing Cr content the magnetic order changes from antiferromagnetic to ferromagnetic. Hardened compounds exhibit a thermal hysteresis in the vicinity of the magnetic phase transition, what is characteristic for a first-order magnetic phase transition. The magnetic phase transition temperatures are decreased as a result of quenching of the samples. The magnetic entropy changes were calculated using the field dependences of isothermal magnetization in terms of the thermodynamic Maxwell relation. The magnetic entropy changes, |ΔSMmax|, obtained for the hardened alloys with x = 0.25 have the maximum value equal to 23 J/(kg·K) near the magnetic phase transition for a field change of ΔH = 0–60 kOe.