The antiferromagnetic structure of ErCo2Si2 by neutron diffraction

The magnetic structure of the tetragonal ErCo₂Si₂ compound is determined by neutron diffraction on powder sample at 4.2 K. The magnetic ordering is connected with a symmetry lowering, magnetic space group P_2s$\text{1}$ (Sh⁷₂)k = 000. The structure is collinear antiferromagnetic with the erbium magnetic moments making an angle of 56.2° with the c axis. The magnetic moment value for erbium is 6.75μ_B.     

The canted ferrimagnetic structure of Nd5Ge4 by neutron diffraction

The chemical and magnetic structures of the intermetallic compound Nd₅Ge₄ were determined from neutron diffraction powder data. In contrast to the isomorphous heavy rare-earth compounds, Nd₅Ge₄ orders with a canted ferrimagnetic arrangement below T_c = 52 K. The ordered Nd moments are 2.6, 3.1 and 2.4 μ_B for the three sites respectively. The magnetic space group is Pnm'a' and the plane of easy magnetization (010).     

Neutron diffraction study of DyCu2Ge2

The DyCu₂Ge₂ compound was studied by neutron diffraction on the Grenoble Nuclear Research Center multicounter system. The compound is isostructural to the rare earth RCu₂Ge₂ compounds with space group I4/mmm. 19 superlattice lines were observed in the 3 K pattern which are consistent with a doubling of the unit cell in the a and c directions. The moment value is 8 μ_B making an angle of 30° with a and 70° with c axis. The structure consists of ferromagnetic (1 0 1) layers with antiferromagnetic coupling between them. The Néel and Curie paramagnetic temperature of this compound is 8 K and ? 15 K respectively.     

Magnetic properties of Nd5Ge3 studied by neutron diffraction and magnetic measurements

Nd₅Ge₃ crystallizes in the hexagonal, Mn₅Si₃ type structure and orders antiferromagnetically at (52±2) K with a collinear double sheet structure fro the Nd atoms at the 6 (g) position and a canted structure for the 4(d) atoms. The main axis of antiferromagnetism is parallel to the c direction. The ordered saturation moments for both Nd positions (1.39 and 1.34μ_B, respectively) are below the free ion value gJ = 3.27 μ_B, due to crystal field effects. At temperatures below about 20 K a comparatively strong ferromagnetic component can be induced by means of an external field. From the constricted shape of the hysteresis loop it is derived that the corresponding spin flop transition is stronly hysteretic in character.     

Neutron diffraction study of magnetic ordering in PrCu2Si2, PrCu2Ge2, PrFe2Ge2 and NdFe2Ge2

A neutron diffraction study of polycrystalline PrCu₂Si₂ [1], PrCu₂Ge₂ [2], PrFe₂Ge₂ [3] and NdFe₂Ge₂ [4] intermetallics carried out at liquid helium temperature shows the presence of a collinear antiferromagnetic order below T_N = 19 ± 1 K [1], T_N = 16 ± 1 K [2], T_N = 9 ± 1 K [3] and 13 ± 1 K [4]. Magnetic moment, parallel to the c-axis is localized on RE ions only. The magnetic structure of these compounds consists of ferromagnetic layers perpendicular to the c-axis coupled antiferromagnetically with sequence +-+- for PrCu₂Si₂ and PrCu₂Ge₂ and +--+ for PrFe₂Ge₂ and NdFe₂Ge₂. The RE moments amount close to the free ion values for Fe containing compounds but are smaller in those containing Cu suggesting a fairly strong influence of crystal field.     

A powder neutron diffraction study of the ErCu2Ge2 compound - crystal field

The compound ErCu₂Ge₂ was studied by neutron diffraction. The diffraction diagram of this compound at 170 K agrees with its crystallographic structure. Its diagram at 1.9 K reveals the existence of superlattice lines consistent with a cell doubled in the a and c directions. The erbium magnetic moment (8.0±0.4)μ_B lies on the c-axis. Crystal field calculations on the Er³⁺ site give 7.9μ_B, with easy magnetization axis the c-axis of the crystal. Copper must contribute to the V^m_l crystal field parameters with a charge equal to 0.6⁺.     

Magnetic properties of NdCo2Ge2, ErCo2Ge2 and PrFe2Ge2 compounds

Magnetometric and neutron diffraction studies of polycrystalline NdCo₂GE₂, ErCo₂Ge₂ and PrFe₂Ge₂ compounds were carried out in the temperature range between 4.2 and 300 K. All samples are antiferromagnetic with Néel temperature 26.5, ～ 4.2 and 13 K, respectively. The RECo₂Ge₂ compounds have collinear antiferromagnetic order of +?+? type. For PrFe₂Ge₂ a sinusoidal magnetic structure is observed. Magnetic moment is localized on RE atoms only and is equal to that of RE³⁺ free ion value. In ErCo₂Ge₂ the magnetic moment of Er atoms is perpendicular to the c-axis, whereas for remaining compounds it is parallel to the c-axis.     

Magnetic structure determination of NdNiC2 and TmNiC2 by neutron diffraction

Isostructural orthorhombic NdNiC₂ and TmNiC₂ reveal collinear antiferromagnetic structures with magnetic propagation vectors [1/21/20] and [0, 0, 1], respectively. In NdNiC₂, ferromagnetic (110) planes are coupled pairwise in opposite spin orientations; in TmNiC₂, adjacent ferromagnetic (001) planes are coupled antiferromagnetically. The magnetic moments are oriented parallel to the a-axis and have values of 2.7μ_B (Nd) and 3.3μ_B (Tm) at 4 K.     

Magnetic structure of FeI2 by neutron diffraction experiments

Phase transitions study of FeI₂ in high magnetic field parallel to the anisotropy axis has proved that FeI₂ has an antiferromagnetic structure (below T_N = 9.3 K) more complex than the two sublattices structure characteristic of FeCl₂ and FeBr₂.We performed neutron diffraction experiments, at room temperature and at 4.2 K using a powder sample. The results show that FeI₂ has an antiferromagnetic structure similar to the structure proposed by Keohler for MnBr₂, but with spins oriented along the crystal anisotropy axis perpendicular to the Fe⁺⁺ layers. This spin orientation is in accordance with the results of parallel and perpendicular susceptibilities study.     

A magnetic study of the ThCr2Si2-type RPd2Ge2 (R=Pr, Nd) compounds. Magnetic structure of PrPd2Ge2 from powder neutron diffraction

The magnetic properties of the PrPd₂Ge₂ and NdPd₂Ge₂ compounds have been investigated by magnetic measurements, specific heat measurements and neutron diffraction experiments. The PrPd₂Ge₂ compound orders antiferromagnetically below T_N=5.0(2) with an original modulated magnetic structure characterized by a magnetic cell three times larger than the chemical one by tripling of the c parameter. The palladium atom is non magnetic and the Pr moments are parallel to the c-axis with a value of ≈2.0 μ_B at 2 K. The specific heat measurements clearly detect a low temperature transition for the NdPd₂Ge₂ compound, interpreted as a Nd sublattice antiferromagnetic ordering below 1.3(2) K.     

Neutron diffraction study of antiferromagnetic sulfur La2MnZnS5

Neutron diffraction experiments show that orthorhombic La₂MnZnS₅ is a helimagnet with propagation vector along [001] leading to a turning angle φ ∽ 108°. Magnetic moments are in (010). Interchain antiferromagnetic interactions are needed to explain the observed results.     

Magnetic neutron diffraction study of UGA3 and UGA2

The magnetic ordering of the intermetallic compounds UGa₃ and UGa₂ has been examined by time-of-flight neutron diffraction, and the nature of the magnetic order of these compounds is confirmed.     

Neutron diffraction study and specific heat of antiferromagnetic NiI2

A neutron diffraction study has been carried out on a sample of powder of NiI₂: the spectrum at 4.2 K shows only a single magnetic line which cannot be indexed on the 2C lattice. Measurements of the specific heat capacity in the region of the transition show the existence of two peaks at the temperatures T₁=76K and T₂=59.5K, which correspond to singularities in the magnetisation.     

Sublattice magnetization and magnetization process in TbCu2

The TbCu₂ compound exhibits antiferromagnetism and has two nonequivalent Tb sites below 54 K (=T_N). The magnetization for the a-axis increases discontinuously at critical field and saturates at high fields. The magnetization process and magnetic moments have been analyzed in terms of the molecular field theory including the crystal-field interaction.     

Neutron diffraction study of magnetic ordering in ErMn2Si2, ErMn2Ge2 and ErFe2Si2

Neutron diffraction study of polycrystalline compounds ErMn₂Si₂, ErMn₂Ge₂ and ErFe₂Si₂ was performed in the temperature range between 1.8 and 293 K. All compounds have tetragonal, ThCr₂Si₂-type crystal structure. The antiferromagnetic collinear structure of ErMn₂Si₂ and ErMn₂Ge₂ at both RT and LNT, consists of a sequence + - + - of ferromagnetic layers of Mn atoms. The magnetic moment of an Mn atom (≈2μ_B) is parallel to the c-axist. At low temperatures (LHT and lower), the ferromagnetic ordering within the Er sublattice is observed. The magnetic moment (μ_Er ≈ 9μ_B) is perpendicular to the c-axis. From the temperature dependence of the intensities of the magnetic peaks, the following values for the Curie temperatures were obtained: (10±5) K for ErMn₂Si₂ and (8.5±3) K for ErMn₂Ge₂. For ErFe₂Si₂ a collinear antiferromagnetic structure of the + - - + type was found, the magnetic unit cell consisting of the chemical one, doubled along the c-axis.     

Neutron diffraction study of antiferromagnetic TbIn3

Observations were on a polycrystalline sample using unpolarised neutrons, at temperatures of 4.2 K and 100 K. There is 1 1 0 antiferromagnetic ordering. The magnetic moment is 7.2±0.4 μ_B, with its direction close to that of the c-axis.     

Kinetic study of NH3/ND3 exchange in TaS2 by neutron diffraction

Tracer exchange of TaS₂·NH₃ by liquid ND₃ was investigated at 215 and 223 K by neutron diffraction. The results suggest only a molecular exchange on the time-scale of quasielastic neutron scattering measurements.     

Magnetostructural phase transitions of DyFe4Ge2: Part II Neutron diffraction

We present the temperature magnetic phase diagram of the compound DyFe₄Ge₂ determined from neutron diffraction data for the entire magnetically ordered regime. DyFe₄Ge₂ undergoes at a simultaneous structural and magnetic transition of second order (or weakly first order) followed by two subsequent isostructural first-order magnetic transitions at and T_ic1=28K:

The re-entrant lock-in magnetic phase is stable in the high-temperature range T_ic2–T_N and in the low-temperature range 1.5 K–T_ic1 while the incommensurately modulated magnetic phase is sandwiched in the intermediate range T_ic1–T_ic2 between the two commensurate phases. The wave vector q₂ has a temperature-dependent length with a minimum in the middle of the incommensurate range and corresponds to a multiaxial amplitude modulated phase. Symmetry analysis leads for both propagation vectors in Cmmm to a twofold and fourfold splitting of the tetragonal Dy 2b site and the Fe 8i sites, respectively. The low temperature and the phases correspond to 3D canted magnetic structures described by the irreducible representations (Irreps) Γ₂+Γ₃ while the high-temperature q₁ phase to 2D canted magnetic structures described by a single Irrep Γ₂. The T_ic2 transition is connected with reorientations of both Fe and Dy moments.