Search

A monoclinic Y0.7Er0.3Fe2D4.2 compound exhibits unusual magnetic properties with different field induced magnetic transitions. The deuteride is ferrimagnetic at low temperature, and the Er and Fe sublattices present magnetic transitions at different temperatures. The Er moments are ordered below TEr = 55 K, whereas the Fe moments remain ferromagnetically coupled up to TM0 = 66 K. At TM0, the Fe moments display a sharp ferromagnetic–antiferromagnetic transition (FM–AFM) through itinerant electron metamagnetic behavior very sensitive to any volume change. Y0.7Er0.3Fe2D4.2 becomes paramagnetic above TN = 125 K. The pressure dependence of TEr and TM0 has been extracted from magnetic measurements under hydrostatic pressure up to 0.49 GPa. Both temperatures decrease linearly upon applied pressure with dTEr/dP = −126 and dTM0/dP = −140 K GPa−1 for a field of B = 0.03 T. Both magnetic Er and ferromagnetic Fe orders disappear at P = 0.44(4) GPa. However, under a larger applied field B = 5 T, dTM0/dP = −156 K GPa−1, whereas dTEr/dP = −134 K GPa−1 showing weaker sensitivity to pressure and magnetic field. At 2 K, the decrease of the saturation magnetization under pressure can be attributed to a reduction of the mean Er moment due to canting and/or a crystal field effect. Above TM0, the magnetization curves display metamagnetic behavior from an AFM to FM state, which is also very sensitive to the applied pressure. The transition field Btrans, which increases linearly upon heating, is shifted to a lower temperature upon applied pressure with ΔT = −17 K between 0 and 0.11 GPa. These results show strong decoupling of the Er and Fe magnetic sublattices vs temperature, applied field, and pressure. [ABSTRACT FROM AUTHOR]

Structural, magnetic, and electrical properties have been studied on a U3Fe4Ge4 single crystal under hydrostatic pressure. The orthorhombic crystal structure is found to be stable up to 30 GPa, the highest applied pressure, but the compressibility is strongly anisotropic. Contrary to typical uranium intermetallics for which the softest lattice direction is along the shortest inter-uranium links, in U3Fe4Ge4 the lattice is compressed most in a perpendicular direction for the high pressure range. The elastic properties are modified considerably in the vicinity of 1 GPa when the b axis is transformed from least compressible to most compressible. The bulk modulus is found to be about 150 GPa. The anomalies in the elastic properties are reflected in the electronic properties that consistently indicate a change of the magnetic ground state from ferromagnetic to antiferromagnetic. Both types of order exhibit a gap in the magnon spectrum; however, it is twice as high for the ferromagnetic state. The magnetoresistance reveals field-induced transitions of different origins in the antiferromagnetic state along the easy and hard magnetization directions. [ABSTRACT FROM AUTHOR]

We present here a detailed investigation of the pressure dependence of the structural and magnetic properties in a wide temperature range from 5 to 340 K for the Y1-xThxCo4B series. The unit cell lattice compressibility has been determined from powder neutron diffraction technique in the 0 to 0.5 GPa pressure range. Substitution of Th for Y is found to reduce significantly the compressibility. The Curie temperature decreases dramatically upon the Th for Y substitution. Studies were performed on polycrystalline samples under hydrostatic pressure up to 1.1 GPa and in magnetic field up to 5 T. The evolution of the saturation magnetization under pressure is presented as well as the pressure dependence of the Curie temperature. Remarkable pressure effects on the Curie temperature and on the critical field at which the first order magnetization process occurs for Y0.8Th0.2Co4B are analyzed and discussed. The pressure derivatives values of both the Curie temperature and the magnetization are negative for all the studied compounds. This is an opposite tendency than that expected from chemical pressure effects. This supports the dominant role of valence electrons in the magnetic properties of the substituted Y1-xThxCo4B compound in the case of the chemical pressure effect. The magnetization and the Curie temperature exhibit different pressure dependence along the Y1-xThxCo4B series of compounds. [ABSTRACT FROM AUTHOR]

The magnetic properties of the ThFe11Cx (x=1.5 and 1.8) compounds have been investigated at ambient and high pressures. The thermal evolution of the saturation magnetization has been determined up to 550 K. These compounds are found to have a reorientation of their easy magnetization axis, which is aligned along the tetragonal c axis at room temperature but lies within the basal plane at 4 K. The reorientation of magnetization results from competing magnetic anisotropy of inequivalent iron sites. The spin reorientation temperatures are 257 and 202 K for ThFe11C1.5 and ThFe11C2, respectively, showing a significant effect of the carbon concentration. The anisotropy parameters have been obtained on both sides of the spin reorientation transition in the 4–300 K temperature range. The effect of pressure on the spin reorientation temperature has been investigated up to 10 kbars. This spin reorientation transition is found to decrease significantly upon increasing pressure with rates of -9.4 and -8 K/kbar for ThFe11C1.5 and ThFe11C1.8, respectively. A magnetic phase diagram is proposed for both ThFe11Cx compounds. [ABSTRACT FROM AUTHOR]

The temperature dependence of the magnetocrystalline anisotropy and the effects of pressure on the intrinsic magnetic properties of the hexagonal DO19 phase of Fe3Ge single crystals have been studied. The easy-magnetization direction is in the basal plane at low temperatures and a spin reorientation transition from plane to axis occurs at 377 K, with increasing temperature. The thermal dependence of the magnetic anisotropy of Fe3Ge has been determined and described in the frame of the Carr model for localized moments. The partial substitution of Fe by Mn, besides reducing both the saturation magnetization and Curie temperature, extends the axial region widely. Pressure has little influence on the magnetic moment but it markedly affects the crystalline anisotropy. The planar character of the anisotropy is indeed reduced in both pure and substituted compounds. The application of high pressure, the partial substitution of Fe by Mn and the increase of temperature have similar effects on the magnetocrystalline anisotropy of Fe3Ge—all induce a reduction of its planar character, favoring a plane to axis spin reorientation transition. [ABSTRACT FROM AUTHOR]

Linear thermal expansion and magnetostriction measurements under a magnetic field up to 20 kOe, applied parallel and perpendicular to the measuring direction and in the temperature range of 10-300 K, have been performed on a Ni[sub 2]MnGa polycrystal. The effects of zero-field cooling and field cooling on both the self-strain (H=0) and the magnetic-field-induced strain (MFIS) have been studied. We have found that the MFIS strongly depends on whether a magnetic field was applied during the cooling process. The applied magnetic field facilitates the growth of specific orientation variants along the field direction as the sample is cooled down through martensitic transformation. However, the application of a field in the martensitic phase induces a negligible motion of twin boundaries. On this basis, the singular point detection technique performed on polycrystalline specimens results in being the easiest and most direct way by which to determine the anisotropy field in this class of materials. The temperature behavior of the anisotropy constant and field has been determined for Ni[sub 2]MnGa. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Highlights • Effect of volume change on anisotropy. • Spin reorientation transition. • High volume stability of the magnetic properties. • Moderate decrease of the Curie temperature with increasing pressure. Abstract The magnetic properties of HoCo 12 B 6 ferrimagnetic compound are investigated versus the magnetic field, temperature and pressure. The magnetic phase diagram exhibits three remarkable temperatures: the ordering temperature T C , the spin reorientation temperature T SR and the compensation temperature T COMP at 147 K, 76 K and 47 K respectively. In HoCo 12 B 6 intermetallic system the spontaneous magnetization resulting from the antiparallel coupling of the magnetic moments of Ho and Co sublattices is pressure insensitive at lowest temperatures whereas it decreases with pressure at temperature range above T SR. The mean Co magnetic moment is small (<0.5 µ B) in the studied compound and exhibits a weak pressure dependence. In addition, significant pressure effects have been observed on both the spin reorientation transition and the Curie temperatures. A value of dT C /dp = −3.5 ± 0.4 K GPa−1 is dominated by the Co sublattice contribution. The spin reorientation transition temperature is also found to decrease versus pressure dT SR /dp = −4.2 ± 0.4 K GPa−1. The compensation temperature where the Ho and Co sublattices have the same magnitude but opposite direction does not vary significantly with applied pressure in the investigated pressure range (up to 1 GPa). The results of pressure dependence of the magnetic properties are compared to earlier results on other R-Co-B borides. HoCo 12 B 6 compound confirmed the remarkably high volume stability of the magnetic properties of the RCo 12 B 6 compounds with the itinerant character of magnetism and low values of both the T C and magnetization. [ABSTRACT FROM AUTHOR]

Presents the results on magnetovolume anomalies in (Fe1-xNix)49Rh51 alloys. Phase transition exhibited from the ferro- to the antiferromagnetic state at temperatures decreasing from 300 to 150 K at ambient pressure.

The effect of hydrostatic pressure on the magnetic properties has been investigated for itinerant-electron metamagnetic Hf 1− x Ta x Fe 2 ( x =0.125 and 0.14) compounds which exhibit a temperature-induced transition from the ferromagnetic (FM) to the antiferromagnetic (AFM) state upon heating. Both the magnetic transition temperature T FM–AFM and the spontaneous magnetization M S decreases with increasing pressure. The application of an external pressure leads also to the strong increase of the AFM–FM transition field μ 0 H cr . The magnitude of the pressure coefficient, dln( T FM–AFM )/d P , is much larger than that of dln( M S )/d P . This extremely large difference between the pressure coefficients is explained by the influence of spin fluctuations on the magnetovolume effects in the compounds Hf 0.875 Ta 0.125 Fe 2 and Hf 0.86 Ta 0.14 Fe 2 . [ABSTRACT FROM AUTHOR]

Highlights: [•] The magnetic structure of LaCo12B6 is determined from neutron diffraction. [•] The magnetic behavior of YCo12B6 and LaCo12B6 are investigated. [•] The Landau coefficients have been derived for both compounds. [•] The effect of applied pressure on the magnetic properties is presented. [ABSTRACT FROM AUTHOR]

In this communication, we compare effects of hydrostatic and chemical pressure on the magnetic properties of La0.67Ca0.33(CoxMn1-x)O3 ceramics. For ceramics with x=0.03, the Curie temperature TC increases under hydrostatic pressure with a slope d Tc/d p=+23.4 K/GPa. The saturated magnetization μs does not change with applied hydrostatic pressure. Chemical pressure was induced by substitution of Co for Mn. The substitution from x=0.03 to x=0.1 reduces the volume of the elementary cell by about 0.28%, but TC decreases from 203.4 to 167 K. The saturated magnetization μs is not affected by this substitution. [ABSTRACT FROM AUTHOR]

The magnetic properties of Y0.6Th0.4Co4B are studied to characterize the magnetic behaviour of the Co sublattice. Assuming that Y or Th has no effect on magnetic properties, one can think this behaviour to remain unchanged in all RCo4B compounds, where R is a non-magnetic element. However, it has been found that YCo4B and ThCo4B have different magnetic properties. Substituting Th for Y in YCo4B induces a decrease in the Curie temperature (from 378(2) to 302(2) K) and a decrease in the saturation magnetization (from 3.0(1) to 1.5(1) μB). Both the change of chemical pressure effect (due to the change of cell volume) and the change of valence could explain this behaviour. In order to isolate the effect of pressure, we synthesized the intermediate substituted compound Y0.6Th0.4Co4B and studied the evolution of its magnetic properties under hydrostatic pressure. We found the sensitivity of the Curie temperature to be dTC/dP=-0.7(2) K/kbar. The results strongly support the dominant effect of valence electrons on the magnetic properties of the Y0.6Th0.4Co4B intermetallic compound. [ABSTRACT FROM AUTHOR]

The magnetovolume and magnetic properties of RCo4B (R—Y, Ce, Gd) compounds under pressure up to 12 kbar have been studied. We determined the volume dependencies of Curie temperatures, magnetization, spin reorientation transitions (for YCo4B), first-order magnetization process (for monocrystalline GdCo4B) and also the pressure induced changes of the volume anomaly connected with the isostructural phase transition of CeCo4B. The results have been used to analyze the influence of rare-earth atoms on the volume dependencies of exchange interactions and magnetic anisotropy of RCo4B compounds. [Copyright &y& Elsevier]

The results of a complementary study of magnetic properties, magnetovolume effects and neutron diffraction studies under pressure in R 2 Fe 17 compounds with non-magnetic R (R - Y, Ce, Lu) are presented. The collinear ferromagnetic phase existing at low temperature in all three compounds is suppressed at high pressures. The critical pressure P C depends on the compound studied ( P C  ≅ 2.5 kbar for Ce 2 Fe 17 , P C  ≅ 3.5 kbar for Lu 2 Fe 17 , P C  ≅ 12 kbar for Y 2 Fe 17 ). Incommensurate non-collinear magnetic structures that replace the ferromagnetic ones under high pressures have similar features - magnetic moments in each layer of atoms (perpendicular to z -axis) are parallel each other, their direction helically changes from layer to layer. A generalised phase diagram of the studied R 2 Fe 17 compounds was determined with use of the recent compressibility data. [ABSTRACT FROM AUTHOR]

Abstract: The experimental study of the pressure effect on magnetization and compensation temperature of ferrimagnetic GdCo2Fe2B in a magnetic field up to 7 T under hydrostatic pressures up to 10 kbar is presented. Due to the mutual antiparallel arrangement of Gd and 3d sublattices and the negligible pressure effect on localized Gd magnetic moment, the observed increase of with pressure can be attributed to the pressure induced decrease of 3d magnetic moments, predominately to the decrease of Fe moment, . The pressure induced increase of is also responsible for the remarkable increase of under pressure . This opens the field to tunablibilty of the . [ABSTRACT FROM AUTHOR]

Pulsed magnetic fields up to 68 Tesla have been used to determine the intersublattice coupling strength and its temperature dependence of GdCo12B6 compound. This compound exhibits ferrimagnetic behaviour below 163 ± 2 K. Two antiferromagnetically coupled sublattices cancel out at compensation temperature at about 48 K. They are carrying magnetization of typically 0.42 μB/Co atom and 7 μB/Gd. The intrinsic magnetic properties of the GdCo12B6 compound have been determined by combining low temperature magnetic measurements in both steady and pulsed magnetic field, as well as isofield studies in steady field. At 4.2 K, the magnetization curve of GdCo12B6 is found to reach the full saturation with sum of both sublattice magnetizations for an applied magnetic field of about 68 T. In addition a detailed study is presented in the whole ordered temperature range on the basis of magnetization curves recorded using pulsed magnetic field up to 60 T. This has enabled to investigate the intersublattice coupling strength and its temperature dependence, a value JCo-Gd/kB = -5.3 ± 0.3 K is derived from the magnetization curves whereas one gets much larger value for JCo-Co/kB = 108 K. [ABSTRACT FROM AUTHOR]

The magnetic properties of polycrystalline Lu2Fe16.5Mn0.5 and Lu2Fe16.3Mn0.7 compounds have been studied under hydrostatic pressure up to 10 kbar in the temperature range of 5-300 K and at magnetic fields up to 5 T. The Lu2Fe16.3Mn0.7 compound is in the ferromagnetic (FM) state, and the Lu2Fe16.5Mn0.5 is in the FM state at low temperatures and in the antiferromagnetic state at high temperatures at ambient pressure. We have revealed that the FM state is very sensitive to volume changes and even moderate pressure is sufficient to complete its suppression. The critical pressures are 4 kbar for Lu2Fe16.5Mn0.5 and 7 kbar for Lu2Fe16.3Mn0.7. The suppression of the FM ground state is observed at practically the same volume of the elementary cell. The pressure induced Néel temperature, TN, of both compounds decreases with increasing pressure, dTN/dp = -2.5 K/kbar and dTN/dp = -3.4 K/kbar, for Lu2Fe16.5Mn0.5 and Lu2Fe16.3Mn0.7, respectively. The remarkable strengthening of the FM ground state by the Mn substitution and its total suppression by external pressure can mainly be attributed to a subtle competition of positive and negative local direct exchange interactions between Fe atoms located at inequivalent structural sites. These interactions are strongly dependent on the interatomic Fe-Fe distances. [ABSTRACT FROM AUTHOR]

The small nonmonotonic changes of the lattice parameters upon the substitution of Mn for Fe in Ce[sub 2]Fe[sub 17] lead to significant changes of the magnetic properties. In order to determine the role of the volume, we made ac susceptibility and thermal expansion measurements on the polycrystalline compounds Ce[sub 2]Fe[sub 16.65]Mn[sub 0.35] and Ce[sub 2]Fe[sub 16]Mn[sub 1] under hydrostatic pressure up to 10 kbar in the temperature range 10-300 K. The substitution of Mn for Fe leads to significant narrowing of the range of stability of the low-temperature ferromagnetic phase characterized by Θ[sub T]=48 K (x=0.35) in comparison with binary Ce[sub 2]Fe[sub 17], where Θ[sub T]=94 K. Applying a relatively small pressure of 1.5 kbar leads to suppression of both the ferromagnetic order and large positive spontaneous volume magnetostriction in Ce[sub 2]Fe[sub 16.5]Mn[sub 0.35]. The pressure effect on Θ[sub T] is significant, dΘ[sub T]/dp=-30 K/kbar. The effect of pressure on the Néel temperature is moderate and increases slightly, with increasing Mn content (dT[sub N]/dp=-2.2 K/kbar for Ce[sub 2]Fe[sub 16.65]Mn[sub 0.35]). No ferromagnetic order was observed in Ce[sub 2]Fe[sub 16]Mn[sub 1] at ambient pressure, but an unexpected reentrant increase of the ac susceptibility was detected at pressures higher than 1.5 kbar below 50 K. It indicates the existence of a pressure-induced ferromagnetic phase at low temperature. The results show not only a strong correlation between the magnetic properties and the lattice volume but also a significant role of the Mn content. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In order to identify the origin of the giant isotope effect observed on the magnetic properties of YFe2A4.2 compounds (A = H, D) and probe the role of the cell volume difference, we have compared the effect of hydrostatic pressure up to 1.0 GPa on the ferro-antiferromagnetic transition temperatures TF-AF and spontaneous magnetization of YFe2D4.2 and YFe2H4.2. Using compressibility value of 0.013 GPa-1 and the remarkably different negative pressure slopes of TF-AF, the existence of critical volume where the ferromagnetism is suppressed at 0 K, VC = 501.7 ± 0.3 Å3, was demonstrated. This consequently established the crucial role of volume on the huge isotope effect observed on the magnetic properties. [ABSTRACT FROM AUTHOR]

To show and to describe a contrast between the magnetic and structural properties of the stoichiometric Ni2MnGa alloy and the off-stoichiometric and the Co-doped Ni-Mn-Ga alloys, we report the effect of high hydrostatic pressure (up to 1.2GPa) on magnetization and the critical temperatures of structural and magnetic transitions in the off-stoichiometric Ni50-xMn25+x+yGa25-y and the Co-doped Ni50-xCoxMn25+yGa25-y Heusler alloys. A huge decrease in their saturation magnetization MM(5K) under pressure was observed with an extreme value of pressure parameter dlnMM(5K)/dP=-56×10-3GPa-1 in the case of the Ni39Co11Mn34Ga16 alloy. The Curie temperature TCA increases under pressure in all the studied alloys. Almost identical values of dTCA/dP=+4.7÷+5.9KGPa-1 point to a normalized steepness of a dependence of exchange interactions on interatomic distances. The values of paramagnetic effective moments, meff, are identical in both structural phases of the alloys and they lie in a narrow interval from 4.6µB to 5.7µB. Furthermore, the Co-doped alloys show a very strong pressure dependence on the structural critical temperature TM-A, with values of dTM-A/dP up to +34KGPa-1, the highest reported values for the Ni-Mn-based Heusler alloys. The results are discussed in light of the fundamental magnetic interactions in the Heusler alloys and from the point of view of a further exploration of their multifunctional applications. [ABSTRACT FROM AUTHOR]

Abstract: We report the magnetic and magnetocaloric properties in Co-doped Ni–Mn–Ga Heusler alloys around the Mn-rich composition Ni50Mn30Ga20. The presence of Co affects profoundly the critical temperatures and alters the exchange interactions of martensite and austenite to different extents; by varying the composition it is possible to tune the critical temperatures and to induce a paramagnetic gap between the magnetically ordered martensite and magnetic austenite, thus giving rise to a reverse magnetostructural transformation. Contrary to the Co-free alloys, the saturation magnetization moment of austenite is strongly enhanced by Co with respect to the martensitic one: thus the magnetocaloric effect turns from direct into inverse. Remarkable values of the magnetic properties related to the magnetocaloric effect, e.g. the saturation magnetization jump at the transformation (ΔM) and the field dependence of the transformation temperature (dT/dH) are reported, together with high positive values of the isothermal magnetic entropy change (ΔS). The conditions for enhancing the magnetocaloric properties and triggering the sign reversal of the magnetocaloric effect are discussed. [ABSTRACT FROM AUTHOR]

We report the effect of high hydrostatic pressure (up to 1.1 GPa) on magnetization and critical temperatures of the magnetic and magneto-structural transitions in the off-stoichiometric In-doped (Ni,Co) 2 Mn(Ga,In) alloys. The magnetization M M (5 K) of their martensitic phase significantly decreases under pressure and the value of dln M M (5 K)/d P = −55 × 10 −3 GPa −1 was observed in the Ni 41 Co 9 Mn 33 Ga 14 In 3 alloy. The temperature of structural transition of the alloys from martensite to austenite, T M-A , shows a strong dependence on both pressure (d T M-A /d P = 60 K/GPa) and magnetic field. The complex mutual dependence of T M-A to both pressure and magnetic field produces a remarkable reduction of the transformation hysteresis. [ABSTRACT FROM AUTHOR]

Complex study of magnetic, magnetocaloric and structural properties of the Ni 2 MnSn and Ni 1.92 Mn 1.56 Sn 0.52 compounds was performed. The stoichiometric single-crystal of Ni 2 MnSn was prepared by Czochralski method. The remarkable pressure effect on the martensitic magnetization and the martensite-austenite transition temperature T M–A was observed in the Ni 1.92 Mn 1.56 Sn 0.52 compound. The coefficient dT M–A /dp reached value of 18 K/GPa. The already low value of martensite magnetization of Ni 1.92 Mn 1.56 Sn 0.52 was further substantially decreased by external pressure, in contrast with pressure almost insensitive magnetization of the stoichiometric Ni 2 MnSn single-crystal. The pulse magnetic field of 58 T invoked the structural transition at temperature 180 K that is of about 100 K below T M–A of Ni 1.92 Mn 1.56 Sn 0.52 at zero field. An anomalous increase of resistivity of the compound has been observed at temperature range below T M–A , however, it does not copy the sharp change of magnetization at T M–A . The obtained results indicate the important role of interatomic distances on the magnetic ordering and electronic structure of the studied Heusler alloys and are in agreement with the Jahn-Teller mechanism of the martensitic transition in these compounds. [ABSTRACT FROM AUTHOR]

Intrinsic magnetic properties and magnetocaloric effect (MCE) have been investigated for Hf 1− x Ta x Fe 2 ( x = 0.125 and 0.175) itinerant-electron compounds which exhibit a temperature-induced transition from the ferromagnetic (FM) to the antiferromagnetic (AFM) state. Upon increasing Ta concentration, the ferromagnetic ordering temperature strongly decreases with decreasing the lattice parameters and both the isothermal magnetic entropy change ΔS M and the adiabatic temperature change Δ T ad are enhanced. An adiabatic temperature change of Δ T ad = 2 and 2.5 K was observed in Hf 0.875 Ta 0.125 Fe 2 and Hf 0.825 Ta 0.175 Fe 2 , respectively, for a magnetic field change of 3 T. Therefore, the partial substitution of Ta for Hf is highly effective in the enhancement of the magnetocaloric effect in Hf 1− x Ta x Fe 2 systems. In addition substitution can be used to tune both the transition temperature but also the magnetic transition from first toward second order type. [ABSTRACT FROM AUTHOR]

Abstract: We present very significant effects of a partial substitution of Ni, Cr and Si for Fe on magnetic and magnetoelastic properties of the mother Lu2Fe17 intermetallics. The ferromagnetic state is stabilized by the substitution in all the Lu2Fe16X (X=Ni, Cr, Si) intermetallics. Their Curie temperature T C is by about 100K higher than the Néel temperature T N of Lu2Fe17. The magnetoelastic phenomena of the Lu2Fe16X single crystals were studied under high hydrostatic pressure using a non-magnetic pressure CuBe cell in a SQUID magnetometer. The effect of pressure on T C of the Lu2Fe16X intermetallics coincides with changes of T C that are induced by hydrogenation in Lu2Fe17H x . Pressure induced changes of saturated magnetization M S of Lu2Fe16X depend on a kind of X-element and generally, they are several times smaller than those in Lu2Fe17. Magnetocrystalline anisotropy of Lu2Fe17 is strongly reduced by the substitution of Cr for Fe only. [Copyright &y& Elsevier]

Abstract: CoCu nanogranular specimens with Co concentration of 5, 9 and 15at.% were produced by annealing the parent melt-spun ribbon at 450 and 600°C for 1h. Their magnetization curves were quantitatively analyzed for the amount of superparamagnetic and ferromagnetic phases in the temperature of measurement ranging from 5 to 300K. For the two lower concentrations and lower temperature of annealing, the great part of particles became already superparamagnetic within this temperature range. The temperature dependencies of both, magnetization measured in ZFC and FC regimes and initial AC susceptibility, indicated the presence of mictomagnetic state in the studied specimens at low temperatures. Analyses of the latter dependencies pointed to antiferromagnetic interactions existing between particles. Temperature dependencies of the coercivity for samples annealed at 600°C were consistent with those published in the literature, whereas these dependencies for samples annealed at 450°C indicated non-monotonous shape possibly reflecting interactions among superparamagnetic particles. [Copyright &y& Elsevier]

The antiferromagnetism at elevated temperatures, characteristic for Lu2Fe17, is also observed in (Lu1−xYx)2Fe17 compounds up to x=0.8 with a gradual decrease of the temperature range of its stability. All compounds exhibit an easy-plane type of magnetic anisotropy. The average Fe magnetic moment and the first anisotropy constant depend weakly on the Y content with a non-linearity probably originating from a non-statistical occupation of Lu sites by Y atoms. [Copyright &y& Elsevier]

We present the results of crystal structure and magnetization studies of three single crystals grown from melts of different nominal compositions in the vicinity of the Lu2Fe17 stoichiometry. The ferromagnetic state of the crystals is strongly dependent on the real sample composition and the local atomic ordering. A drastic difference is observed in the behaviour of the ferro–antiferromagnetic transition, even in crystals for which almost identical composition and crystal parameters were determined by microprobe and X-ray analysis. [Copyright &y& Elsevier]

• Divergent values of pressure effects on magnetic properties of the off-stoichiometric Ni-Mn-Sn were observed. • Pressure effects confirm recent quantum mechanical calculation of effects of point-defects. • No changes of exchange-spring and exchange-bias effects were detected under pressure. Pressure study of the Heusler Ni 2 MnSn-based alloys revealed divergent values of the pressure effects on magnetic properties within a group of the off-stoichiometric alloys. An increase in temperature of the structural martensitic transition in the Mn-rich alloys under pressure is adequate for volume changes that accompanied the structural transition. An anomalous decrease of electric resistivity of the alloys in vicinity of the structural transition verifies a transfer into ferromagnetic order of the alloys above the transition temperatures. Almost no changes of exchange-spring and exchange-bias effects were detected under pressure in all the studied alloys. All the observed pressure effects are discussed with help of recent quantum-mechanical calculations of effects of multiple point-defects on magnetism of stoichiometric Ni 2 MnSn alloy. [ABSTRACT FROM AUTHOR]