Magnetic structure of Tb2Mn3Si5
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.
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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: 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: The compound Ho2Mn3Si5 exhibits multiple magnetic transitions: (i) an ordering at ∼78 K, (ii) a second magnetic transition at ∼16 K, and (iii) an anomaly at ∼4 K as discussed by the authors.
Abstract: The compound Ho2Mn3Si5 exhibits multiple magnetic transitions: (i) an ordering at ∼78 K, (ii) a second magnetic transition at ∼16 K, and (iii) an anomaly at ∼4 K. Its paramagnetic Curie temperature is found to be small but positive. Assuming a free ion effective paramagnetic moment of 10.6μB for Ho3+ ion, the effective paramagnetic moment per Mn in this compound is calculated to be 1.73μB, which indicates the itinerant nature of Mn d electrons. The various transitions in magnetization data are perhaps due to the ordering of rare earth and Mn moments. The magnetization at 2 K in applied fields of up to 7 T has linear field dependence, indicating dominant antiferromagnetic interactions in the system. Neutron diffraction studies point to a complex amplitude modulated incommensurate magnetic structure at 9 K.
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.
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TL;DR: In this article, the main formulas governing the analysis of the Bragg magnetic scattering are summarized and shortly discussed and the method of profile fitting without a structural model to get precise integrated intensities and refine the propagation vector(s) of the magnetic structure is discussed.
Abstract: In spite of intrinsic limitations, neutron powder diffraction is, and will still be in the future, the primary and most straightforward technique for magnetic structure determination. In this paper some recent improvements in the analysis of magnetic neutron powder diffraction data are discussed. After an introduction to the subject, the main formulas governing the analysis of the Bragg magnetic scattering are summarized and shortly discussed. Next, we discuss the method of profile fitting without a structural model to get precise integrated intensities and refine the propagation vector(s) of the magnetic structure. The simulated annealing approach for magnetic structure determination is briefly discussed and, finally, some features of the program FullProf concerning the magnetic structure refinement are presented and discussed. The different themes are illustrated with simple examples.
11,923 citations
TL;DR: An overall survey of the structural and magnetic features of the La2NiO4+ delta system is presented as a result of neutron diffraction experiments in this article, where a tentative phase diagram is proposed.
Abstract: An overall survey of the structural and magnetic features of the La2NiO4+ delta system is presented as a result of neutron diffraction experiments. The stoichiometric compound ( delta =0) presents two structural phase transitions. At T0 approximately=770 K, La2NiO4 transforms from tetragonal (I4/mmm) to orthorhombic (Bmab); at T1 approximately=80 K, from orthorhombic to a new tetragonal (P42/ncm) phase. Associated with this second phase transition a strong microstrain produces anisotropic broadening of Bragg reflections. La2NiO4 is three-dimensional (3D) antiferromagnetically ordered at room temperature (TN=330 K). A weak ferromagnetic component appears below T1. Oxygen excess suppress the 3D magnetic ordering and the structural phase transformations, giving rise to a non-stoichiometric compound with interstitial oxygens. A tentative phase diagram is proposed.
365 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: Magnetoresistance studies on polycrystalline R2Ni3Si5, (R=Y, rare earth) which order antiferromagnetically at low temperatures, are reported in this paper.
Abstract: Magnetoresistance (MR) studies on polycrystalline R2Ni3Si5, (R=Y, rare earth) which order antiferromagnetically at low temperatures, are reported here. MR of the Nd, Sm, and Tb members of the series exhibit positive giant magnetoresistance, largest among polycrystalline materials (85%, 75%, and 58% for Tb2Ni3Si5, Sm2Ni3Si5, and Nd2Ni3Si5, respectively, at 4.4 K in a field of 45 kG). These materials have, to the best of our knowledge, the largest positive GMR reported ever for any bulk polycrystalline compounds. The magnitude of MR does not correlate with the rare earth magnetic moments. We believe that the structure of these materials, which can be considered as a naturally occurring multilayer of wavy planes of rare earth atoms separated by Ni–Si network, plays a role. The isothermal MR of other members of this series (R=Pr,Dy,Ho) exhibits a maximum and a minimum, below their respective TN’s. We interpret these in terms of a metamagnetic transition and short-range ferromagnetic correlations. The short-range ferromagnetic correlations seem to be dominant in the temperature region just above TN.
18 citations