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Influence of Zr-substitution on magnetic properties of [([Lu.sub.1 - x][Zr.sub.x]).sub.2][Fe.sub.17] single crystals was investigated. The homogeneity range of [([Lu.sub.1 - x][Zr.sub.x]).sub.2][Fe.sub.17] compounds extends from x = 0 to 0.2, since the compound with a higher Zr content, x = 0.4, was found to be multiphase. In [([Lu.sub.0.8][Zr.sub.0.2]).sub.2][Fe.sub.17], antiferromagnetism present in [Lu.sub.2][Fe.sub.17] compound is totally suppressed upon Zr substitution and ferromagnetism is stabilized in the whole range of magnetic ordering with a considerable increase of magnetic ordering temperature from 274 K in [Lu.sub.2][Fe.sub.17] to 325 K in [([Lu.sub.0.8][Zr.sub.0.2]).sub.2][Fe.sub.17. Successful hydrogenation without estroying the single-crystalline structure of [([Lu.sub.0.8][Zr.sub.0.2]).sub.2][Fe.sub.17] compound was performed, and [([Lu.sub.0.8][Zr.sub.0.2]).sub.2][Fe.sub.17][H.sub.0.48] hydride was obtained. Hydrogenation of [([Lu.sub.0.8][Zr.sub.0.2]).sub.2][Fe.sub.17] resulted in increase of [T.sub.C] from 325 K to 365 K. [([Lu.sub.0.8][Zr.sub.0.2]).sub.2][Fe.sub.17][H.sub.y] (y = 0, 0.48) compounds have an easy-plane type of magnetic anisotropy and possess magnetic moments of 35 [[micro].sub.B]/f.u. in the ground state. Influence of Zr doping and effect of subsequent hydrogenation of the [([Lu.sub.0.8][Zr.sub.0.2]).sub.2][Fe.sub.17] compound on magnetocrystalline anisotropy of [Lu.sub.2][Fe.sub.17] compound was found to be rather weak. Index Terms--Hydrides, intermetallic compounds, substitutions.

The antiferromagnetic state seen in [Lu.sub.2][Fe.sub.17] at elevated temperatures is stabilized down to the ground state in [([Lu.sub.0.8][Ce.sub.0.2]).sub.2][Fe.sub.17] and [Lu.sub.2][Fe.sub.16.5][Ru.sub.0.5]. The pressure and substitution effects are understood in terms of exchange interaction varying with changes in the lattice parameter c for [([Lu.sub.0.8][Ce.sub.0.2]).sub.2][Fe.sub.17], while for [Lu.sub.2][Fe.sub.16.5][Ru.sub.0.5], the change in magnetic structure has occurred due to the weakening of the positive exchange interaction as a result of the reduction in the Fe magnetic moments.

The effect of Tb and Al substitution within the rare earth and cobalt sublattices on structural and magnetothermal properties of Dy 0.5 Ho 0.5 Co 2 has been studied. Multicomponent Laves phase alloys Tb x (Dy 0.5 Ho 0.5 ) 1− x Co 2− y Al y ( x = 0, 0.3, 0.4, 0.5; y = 0, 0.25) synthesized using high-purity metals have been studied using X-ray diffraction analysis, heat capacity and magnetocaloric measurements. Dy 0.5 Ho 0.5 Co 2 has a first order phase transition at the Curie temperature T C ≈ 110 K. Both Tb and Al substitution leads to increase of the T C . The increasing Tb content leads to the decreases slightly the MCE and all the transitions near the Curie temperature are of the first order. As for the Al-containing compounds, MCE measurements show that the phase transition type changes from the first to the second-order. The advantage of Tb x (Dy 0.5 Ho 0.5 ) 1− x Co 1.75 Al 0.25 as compared with Al-free alloys is ‘table-like’ behavior of MCE. [ABSTRACT FROM AUTHOR]

The influence of Ru substitution on magnetic properties of Y 2 Fe 17 and Y 2 Co 17 (hexagonal crystal structure) is studied via the magnetization measurements performed on single crystals. With the increase of Ru content, the ferromagnetism in Y 2 Fe 17− x Ru x is suppressed rapidly, and the compounds become antiferromagnetic with characteristic metamagnetic behavior in applied magnetic field. If the ferromagnetism of Y 2 Fe 17 is first enhanced by substitutions of Si and Co for Fe or by interstitial introduction of hydrogen, Ru doping does not lead to an antiferromagnetism but only reduces the Curie temperature of the ferromagnets. In the Y 2 Co 17− x Ru x system, only a monotonous decrease of all magnetic characteristics occurs without any qualitative changes. All the compounds studied exhibit easy-plane magnetic anisotropy. [ABSTRACT FROM AUTHOR]

Abstract: The effects of substitutions of Ru for Fe and Ce for Lu on magnetic and thermal properties of Lu2Fe17 are studied by means of magnetization and specific heat measurements on single-crystalline samples of Lu2Fe17-x Ru x (x = 0, 0.5 and 1) and (Lu0.8Ce0.2)2Fe17. It is shown that both substitutions lead to the suppression of the low-temperature ferromagnetic (F) phase present in the initial Lu2Fe17 compound, resulting in stabilization of the antiferromagnetism in the whole range of magnetic order. An increase of the Sommerfeld coefficient γ is found for both substitution cases. The results are discussed taking into account the interatomic distance variation and the change of the electronic structure upon substitution. Thermal properties of (Lu0.8Ce0.2)2Fe17 and Lu2Fe16.5Ru0.5 are also studied across the metamagnetic transition restoring the F coupling. [Copyright &y& Elsevier]

Abstract: Single crystals of Lu2Co17−x Si x within the homogeneity range of Si substitution for Co (0≤ x ≤3.4) were grown by the Czochralski method. Magnetization measurements have revealed that the parent Lu2Co17 compound has a spin-reorientation transition (SRT) from the easy-plane to the easy-axis at elevated temperatures which occurs as 2 second-order phase transitions, the “plane-cone” at T SR1 ≈670K and the “cone-axis” at T SR2 ≈730 K. The effect of Si substitution for Co on magnetic anisotropy and spin-reorientations of Lu2Co17 was studied. In Lu2Co16Si, the SRTs shift towards lower temperatures (T SR1 ≈75K, T SR2 ≈130K) and disappear for compounds with Si content x >1 where the anisotropy is uniaxial over the whole range of magnetic ordering. A phenomenological discussion of Co sublattice anisotropy, with reference to the model of individual site contribution to magnetic anisotropy (ISA) is provided. [Copyright &y& Elsevier]

Abstract: Magnetization study of intermetallic compounds UFe5Al7 and UFe6Al6 with the ThMn12-type tetragonal crystal structure is performed on single crystals. The compounds are ferromagnets with Curie temperatures of 275K and 315K, respectively, and possess large magnetocrystalline anisotropy of the easy-plane type with the anisotropy field exceeding 20T. It is contributed from the U sublattice, because the Fe sublattice provides the anisotropy by an order weaker. In both UFe5Al7 and UFe6Al6, a noticeable anisotropy within the basal plane is observed with the [110] axis as the easy-magnetization direction, the [100] curve saturates in fields above 1T. The in-plane anisotropy is a next evidence for the U magnetism because it was not observed in Lu analogue. The large anisotropy persists in the paramagnetic state as well, again due to the U sublattice because it is absent in LuFe6Al6. Magnetic moments of the U and Fe atoms are estimated as 1.8μ B and 1.3μ B, respectively. [Copyright &y& Elsevier]

Abstract: Magnetization study of single crystals of hydrides of the intermetallic compound Lu2Fe16.5Ru0.5 revealed that even a low hydrogen content as y =0.6 in Lu2Fe16.5Ru0.5H y suppresses totally the antiferromagnetic (AF) state, stabilizes the ferromagnetism (F) and increases the magnetic ordering temperature from T N =208K to T C =290K. Suppression of the F state (with decrease of T C) and restoration of the AF state (T N =218K) with a low-field metamagnetic transition was observed in Lu2Fe16.5Ru0.5H0.6 under hydrostatic pressures up to 0.9GPa. [Copyright &y& Elsevier]

Abstract: The longitudinal and transverse magnetostriction was measured on a single crystal of U2Fe13Si4 by a capacitor microdilatometer. Anisotropic magnetostriction constants and λ γ,2 of U2Fe13Si4 are found to be in the range (70–210)×10−6 at 4.2K that is high enough to be attributed to the U sublattice. A volume effect observed at the FOMP transition may indicate a field-induced non-collinearity, which involves the exchange magnetostriction to the process in addition to the anisotropic one. The high exchange magnetostriction of U2Fe13Si4 manifests itself in large volume-magnetostriction susceptibility above the technical saturation. [Copyright &y& Elsevier]

Abstract: The homogeneity range of U2Co17−x Si x system with the hexagonal Th2Ni17-type crystal structure extends from x =1 to 3.4. The variation of the magnetic properties within the homogeneity range was studied on single crystals. All the compounds are ferromagnetic, M s and T C decrease monotonously with increasing Si content. The strongly modified magnetic anisotropy of U2Co17−x Si x , as compared to isostructural Lu2Co17−x Si x with the non-magnetic Lu, points to a magnetic state of U up to x =3.0. The U contribution to K 1 decreases with increasing Si content and vanishes at x =3.4 that can be treated as a transition from magnetic to non-magnetic state of U. Spin reorientation was observed with varying temperature in compounds with x ≤3 due to a competition of the U and Co sublattices anisotropies which occurs as two second-order phase transitions of the “plane–cone” and the “cone–axis” type. [Copyright &y& Elsevier]

Lu2Fe17 is a ferromagnet below TC=140 K and antiferromagnet up to TN≈ 278 K. Hydrogen absorption leads to a stabilization in the ferromagnetism over the whole range of magnetic order and to an increase of the ordering temperature up to TC=354 K in Lu2Fe17H1. The external pressure compensates the lattice expansion upon hydrogenation, and a re-entrance of antiferromagnetism is observed. [ABSTRACT FROM AUTHOR]

Abstract: The Co-sublattice anisotropy in Lu2Co17 consists of four competitive contributions from Co atoms at crystallographically different sites in the Th2Ni17-type of crystal structure, which result in the appearance of a spontaneous spin-reorientation transition (SRT) from the easy plane to the easy axis at elevated temperatures. In order to investigate this SRT in detail and to study the influence of Si substitution for Co on the magnetic anisotropy, magnetization measurements were performed on single crystals of Lu2Co17− x Si x (x=0−3.4) grown by the Czochralski method. The SRT in Lu2Co17 was found to consist of two second-order spin reorientations, “easy-plane”–“easy-cone” at T SR1≈680K and “easy-cone”–“easy-axis” at T SR2≈730K. Upon Si substitution for Co, both SRTs shift toward the lower temperatures in Lu2Co16Si (T SR1≈75K and T SR2≈130K) with the further onset of the uniaxial type of magnetic anisotropy in the whole range of magnetic ordering for Lu2Co17− x Si x compounds with x>1 due to a weakening of the easy-plane contribution from the Co atoms at the 6g and 12k sites to the total anisotropy. [Copyright &y& Elsevier]

Abstract: Field and temperature dependencies of the magnetization measured along the principal axes of a U2Co15Si2 single crystal show that this compound is a ferromagnet with a spontaneous magnetic moment of 14.8 μ B per formula unit (at 4.2K), located in the basal plane of the hexagonal crystal structure. A strong easy-plane magnetic anisotropy (K 1=−0.97MJm−3 at 4.2K) is attributed to the U sublattice because Lu2Co15Si2 exhibits easy-axis anisotropy with K 1=0.42MJm−3. The easy-plane anisotropy of U2Co15Si2 transforms to a cone of easy axes above 270K. The magnetization vector approaches the c-axis at 350K, and the compound has easy c-axis anisotropy up to the Curie temperature T C=601K. [Copyright &y& Elsevier]

Abstract: The magnetostriction and thermal expansion of the Er2Fe14BH x (, 2.5) intermetallic compounds were investigated. Measurements were carried out by the strain-gauge method in the temperature range 77–420K in magnetic fields up to 1.2T. It was found that the longitudinal magnetostriction λ ∥(T) of the host compound significantly increases in value in the temperature range 320–365K that mainly connected with the contribution of the Fe-sublattice to the total magnetostriction of the Er2Fe14B. The temperature dependencies of the linear thermal expansion coefficient α(T) measured for the Er2Fe14B compound and for its hydride Er2Fe14BH2.5 have anomalies in the range of the spin-reorientation transition (SRT). It has been shown that Er2Fe14B compound has an invar effect in the temperature range 77–280K. [Copyright &y& Elsevier]

Highlights: [•] Systematic study of structure and magnetic properties of Y2(Fe,Mn)17-H systems was carried out. [•] Main regularities of magnetic behavior of hydrides were determined. [•] Hydrogen reinforces the Fe–Fe exchange interactions and, on the contrary, weakens the Fe–Mn and Mn–Mn ones. [ABSTRACT FROM AUTHOR]

Abstract: Study of magnetostriction of (Lu0.8Ce0.2)2Fe17 has been performed by two methods, bulk and microscopic: by the capacitor dilatometer on a single crystal grown by the Czochralski method and by the X-ray powder diffraction. The field-induced transition from the antiferromagnetic to the ferromagnetic state is accompanied by the lattice expansion both in the basal plane and along the c-axis of the hexagonal structure. In addition to the spontaneous linear magnetostriction , along the a and c axes, respectively, and volume effect ω s =8.4×10−3, a comparable field-induced magnetostriction (λ a =1.3×10−3, λ c =3.4×10−3, ω =6.0×10−3) is observed in a field of 5T applied along the a-axis. [Copyright &y& Elsevier]

Ferrimagnet HoFe 6 Al 6 (tetragonal ThMn 12 -type crystal structure) has a compensation point for the Ho and Fe magnetic sublattices at a temperature close to absolute zero. The experimental study was carried out in fields up to 60 T. H-T phase diagrams and a full magnetization process along the principal crystallographic directions of a single-crystalline sample are obtained theoretically by using a model of a f-d ferrimagnet with two anisotropic sublattices, coupled by weak exchange interaction. The two first-order phase transitions, found experimentally along the [110] and [100] axes, were explained theoretically. The transition along the [110] direction occurs between noncollinear and collinear phases, it starts at the compensation point and ends at a tricritical point around 60 T. The transition along the [100] direction goes also from the point of compensation to the point of the liquid-vapor type at 40 T. This transition was shown to occur between two distinct noncollinear phases. The crucial role of the strong rare-earth anisotropy for the positions of the obtained critical points was revealed. [ABSTRACT FROM AUTHOR]

Abstract: Cubic perovskite SrTi1−x Mn x O3 nanopowders with x = 0–0.5, which is much higher than the conventionally believed Mn incorporation limit, and particles sizes 10–80 nm have been successfully synthesized using the citrate sol–gel method. The crystalline structure, the morphology, the chemical composition and the lattice constant behavior versus the annealing temperature and the Mn concentration have been characterized using X-ray diffraction, scanning electron microscopy and proton-induced X-ray emission techniques. Studies of Raman light scattering and the magnetic properties revealed the activation of the TO2 polar mode and the magnetic ordering effects at low temperatures. Such features are treated as possible evidence of non-d 0 Mn-driven transition to a polar phase with multiferroicity in heavily concentrated perovskite SrTi1−x Mn x O3 nanopowders. [Copyright &y& Elsevier]

Abstract: The magnetization of a Dy2Fe14Si3 single crystal was measured at 4.2K in pulsed fields up to 51T along the principal axes. The compound orders ferrimagnetically at 500K, has a spontaneous magnetic moment of 8μB/f.u. (at 4.2K) and exhibits a very large magnetic anisotropy, 〈100〉 being the easy axis. In fields applied along the 〈100〉 and 〈120〉 axes, field-induced phase transitions are observed at 33T and at 39T, respectively. The c-axis magnetization curve crosses the easy-axis curve at 19T. At higher fields, for all directions, the magnetization continues to increase due to further bending of the sublattice moments. Temperature evolution of magnetic anisotropy and magnetic hysteresis are discussed as well. [Copyright &y& Elsevier]

Abstract: Effect of hydrogen on the magnetic properties of Lu2Fe14B is studied on single crystal samples of the compound and the hydride Lu2Fe14BH2.5. The Curie temperature and the average Fe magnetic moment increase upon hydrogenation whereas the first anisotropy constant decreases. In both the hydride and the parent compound, exhibits a characteristic non-monotonous behavior. [Copyright &y& Elsevier]

Abstract: Effect of hydrogen absorption on the magnetic ordering temperatures in Lu2Fe17− x Si x (0⩽x⩽2) has been investigated. The antiferromagnetic state presented in Lu2Fe17 compound is suppressed and ferromagnetic state is stabilized by the substitution of Si for Fe. A considerable increase of Curie temperature () is observed for both cases: the substitution of Si for Fe and incorporation of hydrogen in the crystal lattice interstices. A relationship between the magnetic properties and unit cell volume in the Lu2Fe17− x Si x H y intermetallic compounds has been analyzed. [Copyright &y& Elsevier]

Abstract: Ground state spontaneous magnetization study for the Y2(Fe1− x Co x )14B and Y2Fe14BH y intermetallic compounds in magnetic fields up to 140kOe have been performed. Obtained results can be summarized as following: the 3d-ion subsystem magnetization (M d) does not increase upon the substitution of Co for Fe even for a small Co content, which is unusual for the Co x Fe1− x alloys or other similar intermetallic compounds, but agrees well with the 3d-band structure for Y2Fe14B, if the density of states picture for the spin-up and spin-down subbands is not changed upon such substitutions (rigid band model). In Y2Fe14BH y the M d increases with the hydrogen content increase. This can be explained by the fact that in the Fe-containing compounds, hydrogen atoms produce low-energy electron states. Leaving the 3d-band 3d electrons transit to these states. This is accompanied by the Fermi level displacement to the “left” and increase in the 3d-band splitting, resulting in the M d rise. [Copyright &y& Elsevier]