Multi-magnetic transitions in Tb2Mn3Si5
TL;DR: In this article, the results of ac magnetic susceptibility, dc electrical resistivity and thermoelectric power measurements on Tb 2 Mn 3 Si 5 compound of Sc 2 Fe 3 Si5 -type structure are reported in the temperature range 20-300 K.
Abstract: The results of ac magnetic susceptibility, dc electrical resistivity and thermoelectric power measurements on Tb 2 Mn 3 Si 5 compound of Sc 2 Fe 3 Si 5 -type structure are reported in the temperature range 20–300 K. The compound is a paramagnet at room temperature and it undergoes a para- to ferrimagnetic transition at around 172±0.5 K ( T C1 ) and enters the ferromagnetic region around 30±0.5 K ( T C2 ). The resistivity shows an insulator to metal-type transition as the material goes from the disordered paramagnetic phase to the ordered magnetic phase. The thermopower is negative at room temperature and it crosses zero at around 132 K displaying a broad maximum centered at 65 K. These successive magnetic transitions are attributed to competitive Mn–Mn inter- and intralayer interactions, characteristic of the layered structure of the compound.
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TL;DR: In this paper, a new compound, Ce2Rh3(Pb,Bi)5, has been grown via a flux-growth technique using molten Pb as a solvent, which is characterized by single crystal X-ray diffraction and found to be of the orthorhombic Y 2Rh3Sn5 structure type with lattice parameters a=4.5980(2), b=27.1000(17), c=7.4310(4)
Abstract: Single crystals of a new compound, Ce2Rh3(Pb,Bi)5, have been grown via a flux-growth technique using molten Pb as a solvent. The compound has been characterized by single crystal X-ray diffraction and found to be of the orthorhombic Y2Rh3Sn5 structure type [Cmc21 (No. 36), Z=4] with lattice parameters a=4.5980(2), b=27.1000(17) and c=7.4310(4) A, with V=925.95(9) A3. Ce2Rh3(Pb,Bi)5 has a complex crystal structure containing Ce atoms encased in Rh–X (X=Pb/Bi) pentagonal and octagonal channels in [100], with polyanions similar to those found in Ce2Au3In5 and Yb2Pt3Sn5. Magnetization measurements find that Ce2Rh3(Pb,Bi)5 is a quasi-two-dimensional system, where the Ce moments are spatially well-localized. Heat capacity measurements show a transition at the Neel temperature of 1.5 K. Evidence for Fermi surface nesting is found in electrical resistivity measurements, and we argue that Ce2Rh3(Pb,Bi)5 is very near a metal–insulator transition in zero field.
9 citations
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.
8 citations
TL;DR: In this paper, the results of ac magnetic susceptibility, dc electrical resistivity and thermoelectric power measurements on Tb 2 Mn 3 Si 5 compound of Sc 2 Fe 3 Si5 -type structure are reported in the temperature range 20-300 K.
Abstract: The results of ac magnetic susceptibility, dc electrical resistivity and thermoelectric power measurements on Tb 2 Mn 3 Si 5 compound of Sc 2 Fe 3 Si 5 -type structure are reported in the temperature range 20–300 K. The compound is a paramagnet at room temperature and it undergoes a para- to ferrimagnetic transition at around 172±0.5 K ( T C1 ) and enters the ferromagnetic region around 30±0.5 K ( T C2 ). The resistivity shows an insulator to metal-type transition as the material goes from the disordered paramagnetic phase to the ordered magnetic phase. The thermopower is negative at room temperature and it crosses zero at around 132 K displaying a broad maximum centered at 65 K. These successive magnetic transitions are attributed to competitive Mn–Mn inter- and intralayer interactions, characteristic of the layered structure of the compound.
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Journal Article•
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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
2,576 citations
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25 Apr 1992
TL;DR: The Rietveld method is described in this article, where structure and lattice parameters are directly refined from powder diffraction data and several functions such as extinction correction, preferred orientation, and profile shape function have been improved to give physical meanings to parameters contained in them.
Abstract: The outline of the Rietveld method is described where structure and lattice parameters are directly refined from powder diffraction data. Several functions such as extinction correction, preferred-orientation function, and profile-shape function, which are contained in the model function, have been improved to give physical meanings to parameters contained in them. Structure-refinement strategy is introduced which may be useful for beginners. Combined refinement of X-ray and neutron diffraction data is now being used more and more widely to extract structural information from powder patterns as much as possible.
502 citations
TL;DR: In this article, the magnetic properties of SmMn2Ge2 with a layer structure have been studied by magnetization measurements using single crystal, and the appearance of successive magnetic orderings are attributed to the variation of the shortest Mn-Mn distance due to thermal expansion and the existence of ferromagnetic coupling between the Sm moments in the intralayer which is dominant at low temperatures.
Abstract: Magnetic characteristics of SmMn2Ge2 with a layer structure have been studied by magnetization measurements using single crystal. In the sequence of decreasing temperature, ferromagnetism is observed at 196 K ≲ T ≲ 348 K, collinear antiferromagnetism becomes stable for 64 K ≲ T < 196 K and reentrant ferromagnetism appears below 64 K. The appearance of such successive magnetic orderings are attributed to the variation of the shortest Mn-Mn distance due to thermal expansion and the existence of ferromagnetic coupling between the Sm moments in the intralayer which is dominant at low temperatures.
163 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