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1.
We report on magnetisation, resistivity and specific heat measurements of R 2Pd 2In compounds synthesised with the nominal composition R 40Pd 41In 19 (R=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y). Magnetic and thermodynamic measurements reveal antiferromagnetic order below 32 K for this series except for Y, La, Yb and Lu. An appreciably wide homogeneity range is found for Ce 2Pd 2+xIn 1−x where ferro- or antiferromagnetic order or both occur with typical features of a Kondo lattice. Yb 2Pd 2In exhibits intermediate valent behaviour and no magnetic order could be detected down to 0.3 K. 相似文献
2.
The title compounds were prepared from the elemental components by arc-melting and subsequent annealing at 1020 K and 1170 K. Both CePd 0.63Ge 1.37 and CeAu 0.75Ge 1.25 crystallize in the AlB 2 structure type with a statistical distribution of the transition metal and germanium atoms on the boron site. The structure of CeAu 0.75Ge 1.25 was refined from single crystal X-ray data: P6/mmm, a=433.5(1) pm, c=422.6(1) pm, V=0.0688(1) nm 3, Z=1, wR2=0.0504 for 157 F2 values and 7 variables. Magnetic susceptibility data for both compounds show a full cerium moment and ferromagnetic ordering at 6.0(5) K for CeAu 0.75Ge 1.25 and 3.0(5) K for CePd 0.63Ge 1.37. The crystal structure and properties of CeAu 0.75Ge 1.25 are compared with those of equiatomic CeAuGe which adopts the NdPtSb structure type, an ordered variant of AlB 2. 相似文献
3.
Magnetic properties of TbFe 2, DyFe 2, Tb(Fe 0.8M 0.2) 2 and Dy(Fe 0.8M 0.2) 2 with M=Co, Al, Si, Ga alloys affected by the Hydrogenation-Decomposition-Desorption-Recombination processing have been studied. After hydrogen treatment the coercive force Hc grows sharply, so HDDR-powders can be used as isotropic permanent magnets with the energy product up to 26 MG Oe at T=77 K. In Dy(Fe 0.8Al 0.2) 2 at T<10 K the stepwise magnetic reversal has been observed. The HDDR-treatment increases the critical field of magnetic reversal from 11 up to 18.4 kOe at 4.2 K. It is shown that the effect of the stepwise magnetic reversal is caused by a heat release in a sample during an avalanche motion of narrow domain walls. 相似文献
4.
Ho 3Pd 4Ge 4 crystallizes in the orthorhombic Gd 6Cu 8Ce 8-type of structure (space group Immm) in which the Ho atoms occupy two nonequivalent crystallographic positions: 2a and 4j. Neutron diffraction measurements indicate that the Ho moments in the 4j site below 6.7 K form a collinear antiferromagnetic structure with the magnetic moments parallel to the a axis, whereas the Ho moments in the 2a site below 5 K form a sine-wave modulated structure with the magnetic moments parallel to the c axis. 相似文献
5.
The paper is focusing on the modification of the crystal lattice upon the hydrogenation of La 2Pd 2In and hydrogen desorption from La 2Pd 2In hydrides. The synthesis at 1 bar of hydrogen produces a crystalline hydride with 1.5 H atoms per formula unit and the volume expansion of Δ V/ V = 6.0%. The synthesis at 10 and 100 bar H 2 pressures leads to an amorphous state and with 4 + δ H atoms/f.u. The uptake of hydrogen leads to the decrease of the Debye temperature of La 2Pd 2In and modification of the optical phonon spectrum. 相似文献
6.
Five novel cerium-based ternaries Ce 2Rh 3.1Si 0.9, Ce 4Rh 12Si, Ce 8Rh 21.9Si 3.1, CeRh 1.82Si 0.18 and CeRh 3Si 0.125 were studied by means of magnetic susceptibility and electrical resistivity measurements. All these phases were found to be Pauli paramagnets with metallic type of electrical conductivity. 相似文献
7.
The ErAu xNi 1−xIn (0 ≤ x ≤ 1) quasiternary compounds crystallize in the hexagonal layered crystal structure of ZrNiAl-type. ErAuIn was reported to be an antiferromagnet with TN = 3 K and magnetic moments having triangular arrangement within the basal plane (the magnetic order is described by the propagation vector ). On the contrary ErNiIn is a ferromagnet with TC = 9 K and magnetic moments pointing along the c-axis. The magnetic ordering in ErAu xNi 1−xIn (0 < x < 1) solid solution, has been investigated by neutron diffractometry in the temperature range between 1.5 and 15 K. Moreover, bulk magnetic measurements have been carried out in the range 1.72–400 K. All alloys of intermediate composition were found to be antiferromagnets with TN between 4.6 and 7 K. Below 2 K their magnetic order is described by the propagation vector and magnetic moments are aligned along the c-axis. However, for alloys with 0.2 ≤ x ≤ 0.7 the propagation vector was found to turn into with increasing temperature. 相似文献
8.
High density polycrystalline CaCd 2Sb 2 and EuCd 2Sb 2 intermetallics are synthesized by Spark Plasma Sintering and their thermoelectric properties are investigated. X-ray diffraction measurements reveal both materials have a structure in space group, containing a small amount of CdSb as a second phase. Thermoelectric measurements indicate both are p-type conductive materials. The figure of merit value of CaCd 2Sb 2 is 0.04 at 600 K and that of EuCd 2Sb 2 is 0.60 at 617 K. Theoretical calculations show that CaCd 2Sb 2 is a degenerate semiconductor with a band gap of 0.63 eV, while EuCd 2Sb 2 is metallic with DOS of 13.02 electrons/eV. For deeper understanding of the better thermoelectric properties of EuCd 2Sb 2, its low temperature magnetic, transport and heat capacity properties are investigated. Its Nèel temperature is 7.22 K, convinced by heat capacity anomaly at 7.13 K. Hall effect convinced that it is a p-type conductive material. It has high Hall coefficient, high carrier concentration and high carrier mobility of +1.426 cm 3/C, 4.38 × 10 18/cm 3 and 182.40 cm 2/Vs, respectively. They are all in the magnitude of good thermoelectric materials. The Eu 4 f level around Fermi energy and antiferromagnetic order may count for the better thermoelectric properties of EuCd 2Sb 2 than that of CaCd 2Sb 2. 相似文献
10.
Magnetic and electrical properties of the RCu 5.1In 6.9 compounds with R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er were investigated in the temperature range 4.2–300 K. Additionally, for the compounds of Gd, Tb and Dy exhibiting magnetic anomalies at low temperatures, the magnetization versus magnetic field up to 14 T was measured at 4.2 K. Investigated compounds follow the Curie–Weiss law with relatively small values of the paramagnetic Curie temperature and the values of effective magnetic moment being in fair agreement with the values for the free ions. The electrical resistivity exhibits metallic character. The results are discussed in terms of the differences and similarities with other rare earth intermetallics. 相似文献
11.
Experimental results of the single-crystal X-ray diffraction, XPS, ac-magnetic susceptibility (ac- χ), dc-magnetization M( T), and electrical resistivity ( ρ) measurements for the hexagonal Th 7Fe 3-type Gd 5Y 2Pd 3 single crystal are presented. Anomalies in (ac- χ), ( T) and M( T)-curves have allowed to establish that Gd 5Y 2Pd 3 undergoes a long-range ferromagnetic-type ordering at TC = 263 K, followed by a spin-reorientation below 190 K. The magnetization data indicate that there is an excess of the magnetic moment for the Gd 3+ ions. The observed XPS, magnetic and electrical resistivity behaviour points to the coexistence of localized magnetism from the magnetic Gd 3+ ions and itinerant ferromagnetism from 4d- and 5d-electron bands. We discuss the magnetic behaviour of the Gd 7−xY xPd 3 solid solutions in terms of three competitive mechanisms: RKKY-interaction, magnetic frustration and spin-fluctuation. 相似文献
12.
A neutron diffraction investigation has been carried out on the trigonal La 2O 3-type ( hP5, space group , No. 164; also CaAl 2Si 2-type) YbMn 2Sb 2 intermetallic. A two-step synthesis route has been tried in this work, and successfully utilised to prepare single phase samples of this compound. This study shows that YbMn 2Sb 2 presents antiferromagnetic ordering below 120 K. The magnetic structure of this intermetallic consists of antiferromagnetically coupled magnetic moments of the manganese atoms, in the Mn1 (1/3, 2/3, ZMn) and Mn2 (2/3, 1/3, 1 − ZMn) sites; the direction of magnetic moments of manganese atoms forming a φ and a θ angle, respectively with the X- and the Z-axis. At 4 K the magnetic moment of the Mn1 atom is μMn = 3.6(1) μB, with φ = 0° and θ = 62(4)°, whilst the Mn2 atom has a magnetic moment μMn = 3.6(1) μB, with φ = 0° and θ = 242(4)°. On the other hand, in this compound no local moment was detected on the Yb site. 相似文献
13.
A new series of R 2PdIn 8 intermetallics, where R = Pr, Nd, and Sm, was prepared by arc-melting the constituents under argon atmosphere and studied by means of X-ray diffraction and magnetic measurements. The compounds crystallize with a tetragonal structure of the Ho 2CoGa 8 type (space group P4/ mmm). At very low temperatures, they order antiferromagnetically, and the Nd-based indide presumably exhibits an additional magnetic phase transition in the ordered region. 相似文献
14.
Neutron diffraction and magnetization measurements have been performed on the Tb 5Si 3 compound (hexagonal Mn 5Si 3-type, hP16, P6 3/ mcm) to understand its magnetic structure and magnetic properties. The temperature-dependent neutron diffraction results prove that this intermetallic phase shows a complex flat spiral magnetic ordering, presenting three subsequent changes in magnetization at on cooling. However, the magnetization data depict two transitions at 72 K ( TN1) and 55 K ( TN2). The extended temperature range between and over which the neutron diffraction patterns slowly evolve might correspond to the high-temperature antiferromagnetic transition at TN1 and low-temperature antiferromagnetic transition at TN2 of the magnetic data. Between Tb 5Si 3 shows a flat spiral antiferromagnetic ordering with a propagation vector K1 = [0,0, ±1/4]; then, between the flat spiral type ordering is conserved, but by two coexisting propagation vectors K1 = [0,0, ±1/4] and K2 = [0,0, ±0.4644(3)]. The terbium magnetic moments arrange in the XY( ab) plane of the unit cell. Below the magnetic component with K1 = [0,0, ±1/4] vanishes and magnetic structure of Tb 5Si 3 is a flat spiral with K2 = [0,0, ±0.4644(3)], only. Low field magnetization measurements confirm the occurrence of complex, multiple magnetic transitions. The field dependence of the magnetization indicates a metamagnetic transition at a critical field of 3 T. 相似文献
15.
In this work we have investigated (Fe 3Ga/TbFe 2) n multilayers grown by sputtering at room temperature. These multilayers exhibit a large coercivity associated to the crystalline TbFe 2 Laves phase. To reduce the coercivity it is necessary to control the crystallization of that material. In this work, we focus on the analysis of the properties of the TbFe 2 layers. In the as-grown heterostructures we have found evidence of nanoaggregates in the TbFe 2 layers. The Fe 3Ga thickness and the thermal treatments have an influence on the volume of these nanoprecipitates. In the annealed samples, when increasing the Fe 3Ga thickness we observe a decrease in the nanoaggregate volume and thus in the coercivity. The experimental results indicate that the crystallization of the TbFe 2 depends on the Tb diffusion promoted by the thermal treatment and on the stiffness factor ( Y/ α) of the Fe 3Ga layer. The magnetostrictive properties are also strongly influenced by the crystallization of the TbFe 2. We have achieved a maximum magnetostriction constant of nearly 550 ppm with a coercive field close to 400 Oe. 相似文献
16.
Ferrites have been studied for several years due to their wide use as magnetic materials for telecommunications, audio and video, power transformers and many other applications. Equimolar mixtures of Fe2O3 and TiO2 were fired in a muffle furnace at 1200 °C for 4 h. Mixed samples were prepared by replacing TiO2 with calculated amounts of CuO (x = 0.2, 0.4, 0.6, 0.8 and 1 mol). The synthesized samples were characterized with X-ray diffraction and their magnetic properties were measured using vibrating-sample magnetometer. The microstructure of the sample was examined using reflected light microscope and scanning electron microscope. The formation of Fe2TiO5, Fe5CuO8, Cu2TiO3 and CuFeO2 phases were detected whereas their magnetic properties increased with increasing the added mole ratio of Cu2+ ions. The isothermal reduction kinetics of synthesized nanocrystallites Ti–Cu mixed ferrite compacts were studied at 500 °C using hydrogen gas. It was found that the reduction rate and the reduction extent increased with increasing the extent of Cu2+ (0.2–1) whereas the maximum reduction extent (100%) was detected for pure Cu ferrite (Cu2+) while the minimum reduction extent (12%) was detected for pure iron titanate (Cu2+ = 0). The magnetic properties showed a drastic improvement upon reduction with hydrogen gas. 相似文献
17.
Z-type hexaferrites doped with Nd 3+, Ba 3−xNd xCo 2Fe 24O 41 ( x = 0, 0.05, 0.10, 0.15, and 0.25), were prepared by solid-state reaction. The effect of the Nd 3+ ions substitution for Ba 2+ ions on the microstructure and electromagnetic properties of the samples was investigated. The results reveal that an important modification of microstructure, complex permeability, complex permittivity, and static magnetic properties can be obtained by introducing a relatively small amount of Nd 3+ instead of Ba 2+. SEM image shows that the grains of the ferrites doped with Nd 3+ were smaller, more perfect and homogeneous than that of the pure ferrite. The real part ( ?′) of complex permittivity and imaginary part ( ?″) increase at first, and then decrease with increasing Nd content. At low frequency, the imaginary part μ″ of complex permeability decreases with Nd content and then increases when frequency is above 7.0 GHz. The magnetization ( Ms) and the coercivity ( Hc) are 79.38 emu g −1 and 36.94 Oe for Ba 2.75Nd 0.25Co 2Fe 24O 41. The data of magnetism show that the ferrite doped with Nd 3+ ions is a better soft magnetic material due to the higher magnetization and lower coercivity. 相似文献
18.
The rare earth-rich compounds Ce 23Ru 7Cd 4 and Pr 23Ru 7Cd 4 were synthesized from the elements in sealed tantalum ampoules in an induction furnace. Both structures were refined on the basis of diffractometer data: P6 3mc, Z = 2, a = 988.7(3), c = 2241.6(5) pm, w R2 = 0.0439, 1976 F2 values for Ce 23Ru 7Cd 4 and a = 992.7(2), c = 2236.4(7) pm, w R2 = 0.0466, 2528 F2 values for Pr 23Ru 7Cd 4 with 74 variables per refinement. Striking structural motifs are ruthenium centered trigonal prisms RuCe 6 and RuPr 6 which are condensed via common edges and corners, building rigid three-dimensional networks. Larger voids within these networks are filled by slightly elongated Cd 4 tetrahedra. Five of the nine crystallographically independent cerium sites in Ce 23Ru 7Cd 4 show Ce–Ru distances which are shorter than the Pr–Ru distances in Pr 23Ru 7Cd 4. This strong hint for mixed cerium valence is supported by the magnetic behavior. Pr 23Ru 7Cd 4 shows Curie–Weiss behavior above 50 K with an experimental magnetic moment of 3.62 μ B/Pr atom, indicating stable trivalent praseodymium. Complex magnetic ordering sets in at 13 K. Ce 23Ru 7Cd 4 shows a reduced magnetic moment of 2.05 μ B/Ce atom. The trivalent cerium atoms show ferro- or ferrimagnetic ordering below TC = 3.6 K. 相似文献
19.
The Nd 11Pd 4In 9 compound was prepared by arc melting of pure metals under an argon atmosphere. Crystal structure was refined from X-ray single crystal diffractometer data (space group Cmmm, a = 14.843(3), b = 22.284(3), c = 3.7857(6) Å, Z = 2, RI = 0.0584, 653 F2 values). It has own structure type and together with Mn 2AlB 2, Cr 3AlB 4, Mo 2FeB 2 and Lu 5Ni 2In 4 structure types belongs to homological series based on AlB 2 and CsCl structure types with common formula R m+nM 2nX m. 相似文献
20.
A.c. susceptibility and magnetization measurements of CAg 2Ge 2 are reported. Two phase transitions at T = 7 and 11 K are detected. The magnetization curve at T = 4.2 K has a two-step character. 相似文献
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