Magnetism and electronic transport in R2Mn3Si5 (R=Dy, Ho and Er) compounds
TL;DR: Magnetic susceptibility, electrical resistivity and thermoelectric power measurements on new rare earth ternary intermetallic R2Mn3Si5 (R=Dy, Ho and Er) compounds were carried out in the temperature range 15-300 K as discussed by the authors.
Abstract: Magnetic susceptibility, electrical resistivity and thermoelectric power measurements on new rare earth ternary intermetallic R2Mn3Si5 (R=Dy, Ho and Er) compounds crystallizing in the Sc2Fe3Si5-type tetragonal crystal structure were carried out in the temperature range 15–300 K. Dy- and Ho-based alloys show two successive magnetic transitions (Dy2Mn3Si5 at 76 and 32 K; Ho2Mn3Si5 at 67 and 19 K) and the Er-based compound undergoes a magnetic transition around 55 K. The electrical resistivity is ferromagnetic metal-like, displaying typical low temperature T2 dependence and a high temperature spin-disorder contribution. Thermoelectric power is negative at room temperature, crosses zero and has a broadened peak feature centered around 50 K indicating a phonon drag effect at low temperatures and it does not have the signature of magnetic ordering. The successive magnetic transitions are suggestive of the presence of competing magnetic interactions in these systems.
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TL;DR: The rare earth ruthenium gallides Ln2Ru3Ga5 (Ln = La, Ce, Pr, Nd, Sm) were prepared by arc-melting of cold-pressed pellets of the elemental components as discussed by the authors.
Abstract: The rare earth ruthenium gallides Ln2Ru3Ga5 (Ln = La, Ce, Pr, Nd, Sm) were prepared by arc-melting of cold-pressed pellets of the elemental components. They crystallize with a tetragonal structure (P4/mnc, Z = 4) first reported for U2Mn3Si5. The crystal structures of the cerium and samarium compounds were refined from single-crystal X-ray data, resulting in significant deviations from the ideal compositions: Ce2Ru2.31(1)Ga5.69(1), a = 1135.10(8) pm, c = 580.58(6) pm, RF = 0.022 for 742 structure factors; Sm2Ru2.73(2)Ga5.27(2), a = 1132.95(9) pm, c = 562.71(6) pm, RF = 0.026 for 566 structure factors and 32 variable parameters each. The deviations from the ideal compositions 2:3:5 are discussed. A mixed Ru/Ga occupancy occurs only for one atomic site. The displacement parameters are relatively large for atoms with mixed occupancy within their coordination shell and small for atoms with no neighboring sites of mixed occupancy. Chemical bonding is analyzed on the basis of interatomic distances. Ln–Ga bonding is stronger than Ln–Ru bonding. Ru–Ga bonding is strong and Ru–Ru bonding is weak. The Ga–Ga interactions are of similar strength as in elemental gallium.
8 citations
TL;DR: In this article, the existence of seven binary compounds ErFe 2, ErFe 3, Er 6 Fe 23, Er 2 Fe 17, ErMn 12, Er 6 Mn 23, and one intermediate solid solution γ(Fe·Mn) have been confirmed in the Er-Fe-Mn system at 773 K.
Abstract: In order to determine the existence of phases and relationships in the Er–Fe–Mn system at 773 K, we have carried out this work mainly by X-ray powder diffraction with the aid of differential thermal analysis and have obtained the conclusions below. The existence of seven binary compounds ErFe 2 , ErFe 3 , Er 6 Fe 23 , Er 2 Fe 17 , ErMn 12 , Er 6 Mn 23 , ErMn 2 and one intermediate solid solution γ(Fe·Mn) have been confirmed in this system. Er 6 Fe 23 and Er 6 Mn 23 form continuous solid solution Er 6 (Fe 23− X Mn X ) (0 ≤ X ≤ 23). At 773 K, the maximum solid solubility of Fe in αMn, ErMn 12 , ErMn 2 phases and Mn in ErFe 2 , Er 2 Fe 17 , αFe phases are about 31, 69, 13 at% Fe and 47, 28, 8 at% Mn, respectively. The homogeneity range of γ(Fe·Mn) phase extended from about 34 at% Mn to 52 at% Mn. The maximum solid solubility of Er in γ(Fe·Mn) phase is about 2 at% Er. The isothermal section consists of ten single-phase regions, sixteen two-phase regions and seven three-phase regions. No ternary compounds were observed at 773 K in this system.
6 citations
TL;DR: In this paper, magnetization measurements have been carried out on the Er 2 Mn 3 Si 5 compound in the temperature range 1.8-300 K and the magnetic susceptibility in the paramagnetic region, above 100 K, follows simple Curie-Weiss type behavior.
Abstract: Magnetization measurements have been carried out on the Er 2 Mn 3 Si 5 compound (tetragonal Sc 2 Fe 3 Si 5 -type, space group P 4/ mnc ) in the temperature range 1.8–300 K. There is a crossover from a room temperature paramagnetic phase to a ferromagnetic phase at 75 K ( T C1 ). A second magnetic transition is observed at 11.5 K ( T C2 ). The magnetic susceptibility in the paramagnetic region, above 100 K, follows simple Curie–Weiss type behavior. The magnetization does not saturate at 2 K even in applied fields of 7 T. Neutron diffraction data collected at 300 and 9.2 K confirm that both the rare earth and the Mn moments in this compound carry magnetic moments. There are two Mn sublattices (Mn1 and Mn2) coupled orthogonal to each other. Both the rare earth and the Mn1 sublattice order along the positive a axis but the Mn2 moments order along the positive c axis, thus leading to a competition of magnetic interactions at low temperatures.
6 citations
TL;DR: In this article, the isothermal section of the Er-Mn-Nd ternary system at 773 K was investigated mainly by X-ray powder diffraction with the aid of differential thermal analysis.
Abstract: The isothermal section of the Er-Mn-Nd ternary system at 773 K was investigated mainly by X-ray powder diffraction with the aid of differential thermal analysis. The 773 K isothermal section of the ternary system consists of 9 single-phase regions, 14 two-phase regions, and 6 three-phase regions. At 773 K, the maximum solid solubility of Er in Nd and Nd in Er is about 20% (atom fraction) Er and 26% (atom fraction) Nd, respectively. Er 6 Mn 23 and Nd 6 Mn 23 form a continuous solid solution. The homogeneity range of δ phase extends from about 38% (atom fraction) Er to 43% (atom fraction) Er. No ternary compounds were observed at 773 K in this system.
6 citations
TL;DR: In this article, magnetic properties of polycrystalline Sc 2 Fe 3 Si 5 -type Tb 2 Mn 3 Si5 compound (space group P4/mnc ) in the temperature range of 1.8-300 K were investigated.
Abstract: Magnetization (M) and neutron diffraction measurements have been carried out on a polycrystalline Sc 2 Fe 3 Si 5 -type Tb 2 Mn 3 Si 5 compound (space group P4/mnc ) in the temperature range of 1.8–300 K. The compound undergoes a transition from a room temperature paramagnetic phase to a ferromagnetic phase at 89 K ( T C1 ). A Curie–Weiss type behaviour is observed in the paramagnetic region at temperatures above 150 K. In this compound, both the rare earth (Tb) and Mn ions carry magnetic moments and there are two Mn magnetic sublattices, one coupling ferromagnetically and the other coupling antiferromagnetically with that of rare earth.
4 citations
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TL;DR: In this paper, the early days of the Rietveld method are described, along with a retrospective view of its application in various areas of physics, such as X-ray and neutron analysis.
Abstract: Introduction to the Rietveld Method 1. The early days: a retrospective view 2. Mathematical aspects of Rietveld refinement 3. The flow of radiation in a polycrystalline material 4. Data collection strategies: fitting the experiment to the need 5. Background modelling in Rietveld analysis 6. Analytical profile fitting of X-ray powder diffraction profiles in Rietveld analysis 7. Crystal imperfection broadening and peak shape in the Rietveld method 8. Bragg reflection profile shape in X-ray powder diffraction patterns 9. Restraints and constraints in Rietveld refinement 10. Rietveld refinement with time-of-flight powder diffraction data from pulsed neutron sources 11. Combined X-ray and neutron Rietveld refinement 12. Rietveld analysis programs Rietan and Premos and special applications 13. Position - constrained and unconstrained powder-pattern-decomposition methods 14. Ab initio structure solutions with powder diffraction data
3,162 citations
TL;DR: In this paper, a Kondo lattice system exhibiting two antiferromagnetic transitions at 5.1 and 4.5 K was investigated by means of transport, specific heat and magnetization measurements.
Abstract: Our investigation of ${\mathrm{Ce}}_{2}{\mathrm{Ni}}_{3}{\mathrm{Ge}}_{5}$ by means of transport, specific heat and magnetization measurements shows that the compound is a Kondo lattice system exhibiting two antiferromagnetic transitions at ${T}_{N1}=5.1\mathrm{K}$ and ${T}_{N2}=4.5\mathrm{K}.$ An analysis of the transport and specific heat data suggests that the Kondo energy scale ${k}_{B}{T}_{K}$ is of the order of ${k}_{B}{T}_{N}.$ The resistivity and heat capacity data below 4 K are suggestive of the appearance of a spin-wave gap. The compound exhibits giant magnetoresistance at low temperature. The crystal field splitting is estimated to be about 180 K.
55 citations
TL;DR: It is concluded that Ce2Ni3Si5 is a Ce-based valence-fluctuation compound that is nearly temperature independent above 120 K unlike that of a normal metallic material.
Abstract: The results of electrical resistivity (4.2--300 K), magnetic susceptibility (5--300 K) and specific heat (2--20 K) are reported on the ternary orthorhombic rare-earth compound ${\mathrm{Ce}}_{2}$${\mathrm{Ni}}_{3}$${\mathrm{Si}}_{5}$. The resistivity of the material is nearly temperature independent above 120 K unlike that of a normal metallic material. The magnetic contribution to resistivity shows a broad maximum around 200 K. At low temperatures, the resistivity follows a ${\mathit{T}}^{2}$ behavior in the temperature range 4--13 K. The inverse magnetic susceptibility deviates from Curie-Weiss behavior below 80 K where it exhibits a broad maximum in the \ensuremath{\chi} vs T curve. Specific heat measurements (2--20 K) give a value of \ensuremath{\gamma}\ensuremath{\approxeq}62 mJ/Ce mol ${\mathrm{K}}^{2}$ which is similar in magnitude to those encountered in valence-fluctuating systems. From these observations we conclude that ${\mathrm{Ce}}_{2}$${\mathrm{Ni}}_{3}$${\mathrm{Si}}_{5}$ is a Ce-based valence-fluctuation compound.
45 citations
TL;DR: In this paper, positive giant magnetoresistance (GMR) was reported in polycrystalline antiferromagnetic materials RE2Ni3Si5 (RE=Tb, Sm, Nd); Δρ/ρ, at 4.4 K and in a field of 45 kOe, is 85%, 75%, and 58%, respectively.
Abstract: Positive giant magnetoresistance (GMR), Δρ/ρ, is reported here in polycrystalline antiferromagnetic materials RE2Ni3Si5 (RE=Tb, Sm, Nd); Δρ/ρ, at 4.4 K and in a field of 45 kOe, is 85%, 75%, and 58%, respectively. Positive GMR of such large magnitude has not been reported earlier in magnetically ordered polycrystalline compounds. The observed GMR is not correlated to the RE‐moments. It is, however, associated with the magnetic ordering of the lattice as its magnitude is significantly reduced in the paramagnetic state. Surprisingly, MR in Y2Ni3Si5, a non‐magnetic rare earth analogue, is also relatively large (16% at 4.4 K; 45 kOe) and is even slightly higher than that of antiferromagnetically ordered Gd2Ni3Si5 (12% at 4.4 K; 45 kOe). The layered structure of the materials is suggested to be responsible for the observed GMR.
44 citations
TL;DR: In this article, the structural details for Y 2 Ni 3 Si 5 have been determined and the structure was refined to wR = 0.074 for 422 independent reflections, which can be interpreted as an intergrowth of two kinds of structural slabs, one related to the CaBe 2 Ge 2 structure and the other is related to BaNiSn 3 structure.
Abstract: The following structural details were determined for Y 2 Ni 3 Si 5 : M r = 494.37 (orthorhombic); space group, Ibam ; a = 9.5651(4) A ; b = 11.1284(6) A ; c = 5.6453(2) A ; V= 600.91(8) A 3 ; Z = 4; D x = 5.465 Mg m −3 ; Mo Kα, λ = 0.71069 A ; μ (Mo Kα ) = 29.8 mm −1 ; F (000) = 928; T = 293 K . The structure was refined to wR = 0.074 for 422 independent reflections. Ce 2 Co 3 Si 5 , Ce 2 Ni 3 Si 5 and Dy 2 Ni 3 Si 5 have the same crystal structure which is known as the U 2 Co 3 Si 5 type. This structure type can be interpreted as an intergrowth of two kinds of structural slabs, one of which is related to the CaBe 2 Ge 2 structure and the other is related to the BaNiSn 3 structure. The U 2 Co 3 Si 5 and the Sc 2 Fe 3 Si 5 structure types are different stacking variants of identical structural columns.
43 citations