High-field magnetic phase diagram of CsCoCl3 revised

A fine structure of high-field magnetization curves of CsCoCl₃ and related compounds is discussed. It is shown that a precursor of a high-field phase transition originates from nucleation of an intermediate high-field ferrimagnetic (IFM) phase. Since the IFM state is degenerate its growth starting from few nucleation centers gives rise to domain walls formation. Their creep also makes a contribution to the magnetization dynamics similar to slow relaxation in Ca₃Co₂O₆. An experimental verification of the model is proposed.     

A neutron diffraction study of the magnetic properties of PrTiO3 and NdTiO3

The magnetic properties of PrTiO₃ and NdTiO₃ were studied by neutron diffraction at several temperatures below 110 K. Although PrTiO₃ exhibits a T_N at 90 K no significant magnetic scattering was detected down to 65 K. The order at 90 K can be attributed to the Ti(III) below our detection limit of 0.25μ_B. Below 65 K magnetic reflections due to the Pr(III) sublattice develop consistent with a F_xC_y configuration. At 7 K the moment is 1.35(15)μ[inB] and lies at 45° (5) to the a or b axes. This structure is contrasted with that found for PrCrO₃. By comparing powder data at 50 and 7 K for NdTiO₃ it is concluded there is no evidence for magnetic order on either the Nd(III) or Ti(III) sublattices in agreement with bulk magnetic properties. The decrease in magnitude of the Ti(III) moment from LaTiO₃ to NdTiO₃ is compared to the known behavior of the La_1-xY_xTiO₃ system and is found to be consistent.     

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.     

The determination of the magnetic structure of DyCrO4 by neutron diffraction

At room temperature DyCrO₄ has the tetragonal zircon structure. Susceptibility measurements show that DyCrO₄ is ferromagnetic below 23 K. Neutron diffraction from a powder sample yield the magnetic structure. Using a computer program, which was developed for the determination of non-collinear and spiral structures, several models allowed by symmetry were compared with the experiment. It turns out that the Dy-moments and the Cr-moments as well order parallel in the a-b-plane. For the Dy-moment a value of 12μ_B and for the ratio of the Cr- to the Dy-moment a value of $\text{1}\text{10}$ was found.     

Inelastic neutron scattering study of multimagnon states in the 1-D-ferromagnet CsNiF3

Two theoretical propositions concerning scattering from higher-order-spin-wave processes have been tested by means of neutron scattering. The so-called “second magnon” scattering could not be observed as such, and an upper limit for its intensity relative to the single-spin-wave scattering is given. Experimental evidence for the scattering from the simultaneous creation of two spin waves has been observed. The results are compared with the corresponding theories.     

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.     

A neutron diffraction study of the GdA103 magnetic structure

Neutron diffraction experiments have permitted to determine the magnetic order in the GdA10₃ perovskite compound. GdA10₃ is a simple two-sublattice antiferromagnet well described by the Gx-mode. This ordering results from isotropic and negative next neighbours exchange interactions which are more important than dipolar interactions.     

Crystal-field levels in UBr3 determined by neutron spectroscopy

Inelastic neutron scattering experiments have been performed in UBr₃ in order to determine the crystal-field levels. Four transitions between the ground state and all excited states have been observed, thus the crystal-field level scheme could be unambigously assigned. The Russell-Saunders coupling scheme has been used to derive the crystal-field parameters which cannot be accounted for by a simple point charge calculation.     

Low-temperature neutron diffraction study of the crystal and magnetic phase transitions in DyCrO4

The crystal and magnetic structures of DyCrO₄ were studied using neutron powder diffraction. Complete diffraction data at 3.6, 17, 27, and 40 K show that a crystal structural phase transition from tetragonal I4₁/amd to orthorhombic Imma symmetry is found to take place between 27 and 40 K. This transition does not involve a significant change in the unit cell volume. Strong ferromagnetic reflections are observed at 3.6 and 17 K, and can be fit well using the magnetic model of space group Im'ma', with the moments of both Dy³⁺ and Cr⁵⁺ ions aligning along the y-axis. Detailed temperature dependent magnetic intensities of 101/011 and 211/121 peaks reveal a Curie temperature of T_c=22.35(15) K.     

Some structural and magnetic properties of 239PuD2.25 by neutron diffraction

A neutron powder diffraction study of ²³⁹PuD_2.25 compound was performed at different temperatures, in order to determine the deuterium atoms positions and to study the occurrence of structural and magnetic phase transitions. Vacancies of tetrahedral sites were found together with partial occupancy of octahedral special positions. No order disorder transitions were observed at low temperature. Below T = 60 K PuD_2.25 becomes ferromagnetically ordered with an ordered magnetic moment μ_ord = 0.8 μ_B per Pu atom.     

Structure of the low-temperature phase of Rb3D(SeO4)2 by single-crystal neutron diffraction

Crystal structure of Rb₃D(SeO₄)₂ has been investigated at 25 K (below the transition temperature T_c=95.4 K) by single-crystal neutron diffraction. Accompanying the transition, the SeO₄ groups, which are all equivalent in the phase above the transition (space group A2/a), split into eight nonequivalent groups in a superlattice (a×2b×2c, space group A2) in the low-temperature phase. Based on the D atom positions obtained, each of the SeO₄ groups was identified to be in the state closer to a HSeO₄⁻ ion or to a SeO₄²⁻ ion and the dipole arrangement of SeO₄-D-SeO₄ dimer was revealed. This dipole arrangement has ‘ferri’ structure along the polar b-axis, but ‘antiferro’ structure in the plane perpendicular to the b-axis. These results are consistent with the characteristics found in the earlier dielectric measurements.     

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.     

Dynamical critical slowing down in CsNiF3

Dynamical critical slowing down in CsNiF₃ is studied using the a.c. susceptibility measurements at 9.5 GHz in zero external static magnetic field. The dynamical critical exponent for the relaxation time of the in-plane spin fluctuations is obtained for the temperature interval 6 K < T < 20 K. For this temperature interval where one-dimensional spin fluctuations are dominant, very good qualitative and quantitative agreement with the spinwave calculation of the dynamical response is obtained at long wavelength and low frequency. The dynamical critical exponent for the relaxation time is measured to be 0.96 ± 0.6. At higher temperature, a gradual crossover to an isotropic Heisenberg chain behaviour is observed. For temperatures close to the 3-d antiferromagnetic ordering temperature T_N, a crossover to 3-d fluctuation regime gives rise to a speeding-up of the spin relaxation rate.     

The magnetic structures of NdCu2 determined by single crystal neutron diffraction

We investigated the magnetic structure of NdCu₂ by means of neutron diffraction as a function of temperature between 1.5 K and 8 K in zero external field. The diffraction data were obtained on two single crystals with different orientations using the triple-axis-spectrometer TAS6 at the DR-3 reactor at Risø. Two magnetic phases were observed between 1.5K andT _N =6.5K. From 1.5 K to 4.1 K the magnetic reflections can be described by the commensurate wave vector =(3/5 0 0) and its higher harmonics 3 and 5. Below 2.5K the structure is completely squared-up. For 4.1 KT6.5 K the magnetic structure is incommensurate with the chemical lattice and can be described by the wave vector=(3/5 0 0) and its higher harmonies 3 and 5M. Below 2.5 K the structure is completely squared-up. For 4.1 K T 6.5 K the magnetic structure is incommensurate with the chemical lattice and can be described by the wave vector ^*=(0.62 0.044 0). In both phases the Nd-moments are oriented along the easyb-direction.     

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.     

Magnetic phase diagram of Ni(NO3)2 6NH3

The magnetic phase diagram of Ni(NO₃)₂6NH₃ was determined from the field and temperature dependence of the magnetic susceptibility. The zero temperature exchange and anisotropy fields were determined to be H_E(0) ≈ 26 kOe and H_A(0) ≈ 0.7 kOe respectively.     

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 the MnPd3 phase

The magnetic structure of MnPd₃ has been refined using improved crystal structure data for the I4/mmm space group. The magnetic moment on Pd atoms coupled antiparallel to the Mn moments of 4.1 ± 0.3 μ_B was found by neutron diffraction to be 0.15 ± 0.03 μ_B in the 4(c) and 4(e) positions. The Pd moments on the 4(d) sites are assumed to be zero on symmetry grounds.