Neutron diffraction and magnetic measurements for the LaFe13−xGaxC compounds (x=2.9 and 6.5) were carried out in order to investigate their magnetic state. The LaFe10.1Ga2.9C compound is a collinear ferromagnet with magnetic moments of the Fe atoms parallel to the c-axis at T<410K. An average value of the Fe magnetic moments is (2.0±0.1) and (1.9±0.1)μB at 4.2K according to neutron diffraction and magnetic data, respectively. In the LaFe6.5Ga6.5C compound, coexistence of antiferromagnetic regions and spin-glass behavior at T<86K is observed. The Neel temperature of antiferromagnetic regions and the temperature of spin-glass freezing coincide. A model of the antiferromagnetic arrangement of the Fe-atom magnetic moments has been proposed.

X-ray diffraction analysis was used to study the structural state of samples of lanthanum manganite La(0.85)Sr(0.15)Mno(3) irradiated at T-irr approximate to 340 K with fast neutrons to a fluence of 8 X 10(18) cm(-2). The study was performed on powder samples prepared from an irradiated single crystal. It was shown for the first time that the irradiation with fast neutrons to a relatively low fluence causes a transformation of the initial orthorhombic phase into a pseudocubic phase.

Phase transformations induced by pulsed shock-wave loading in a single crystal of the nickel superalloy have been studied. The crystal was loaded by an impact with a steel plate (the maximum pressure on the sample surface was 100 GPa, and the pulse duration was 10 mu s) and by the deceleration of explosion products at an obstacle (the maximum pressure was 20 GPa, and the pulse duration was 10 mu s). Depending on the loading conditions, various pressure-drop gradients behind the shock front were realized. After loading at 20 GPa, the crystal has a high dislocation density; after loading at 100 GPa, a banded structure with misorientation bands directed along the < 111 > directions is formed. X-ray diffraction, neutron diffraction, and high-resolution transmission electron microscopy of the crystal subjected to shock-wave loading reveal an L1(2) -> D0(22) phase transformation in it. Deformation microtwins are observed near microcracks in the D0(22) phase.

The magnetic properties and magnetic structure of the quasi-ternary layered intermetallic Y(Mn1-xVx)(2)Si-2 and La(Mn1-xVx)(2)Si-2 (0 less than or equal to x less than or equal to 0.4) compounds were investigated usin magneticneutronography, magnetic measurements, and measurements of the thermal expansion coefficient. With increasing content of vanadium, the lattice parameter a remains virtually unchanged, while the parameter c and the unit cell volume increase monotonically. With increasing content of vanadium in the La(Mn1-xVx)(2)Si-2 compounds, weakening, of the intralayer ferromagnetic Mn-Mn exchange interactions occurs, which results in an increase in the opening angle of the canted ferromagnetic structure. In the Y(Mn1-xVx)(2)Si-2 compounds, the molecular field of the interlayer Mn-Mn exchange interactions does not change with increasing content of vanadium despite an increase in the interlayer distance and a decrease in the intralayer Mn-Mn exchange interactions which can be considered as the new argument in favor of the fact that the interlayer Mn-Mn exchange interactions in the compounds of the RMn2X2 type are determined by the distance between the manganese atoms within a layer.

Nanocrystalline manganites La0.9Ag0.1MnO3, La0.7Ag0.3MnO3, and La0.7Sr0.3MnO3 have been synthesized by pyrolysis and subjected to isothermal annealing. The atomic, magnetic, and mesoscopic structures of these manganites were investigated using magnetic measurements as well as X-ray and neutron diffraction. Particles of sizes ranging from 30–40 to 600–700 nm coalesced with an increase in the annealing temperature from 600°C to 1300°C. All investigated samples had a rhombohedral structure and were ferromagnetic. The Curie temperature of the samples containing silver decreased while that of the samples containing strontium increased with the annealing temperature (i.e. with the growth in particle size). The magnetization of the Mn ions increased with annealing in all three systems. It is reasonable to assume that the growing size of the nanoparticles lead to an increased magnetization owing to the reduction of the angle between the nearest magnetic moments of the Mn ions.

We have investigated the magnetic structure of TbNi5 using neutron diffraction from 2.2 to 30 K to find new magnetic satellites below TC = 23 K, which have never been reported before. These satellites can be indexed as (0,0,1±τ), (1,0,1±τ), (0,0,2±τ), and (1,0,2±τ), where τ is equal to 0.0194 r.l.u. (reciprocal lattice units). We have observed these new peaks in addition to magnetic peaks seen in previous measurements. We can understand this long-period incommensurate structure in terms of two propagation vectors: k1 = (0,0,0) and k2 = (0,0,τ). From the temperature dependence of the intensity of the commensurate and incommensurate peaks as well as our heat capacity data, we suggest that TbNi5 should have a modulated magnetic structure over the whole temperature range from 23 to 2 K, in contradiction to the long held view that TbNi5 is a collinear ferromagnet below TC = 23 K.

The results of X-ray diffraction. Mossbauer effect and neutron diffraction studies and also magnetic, thermal and kinetic properties measurements of the ternary alloys PdMnxFe1-x are presented, It has been shown that the alloys in the 0.2 < x < 0.8 concentration range realize a micro-inhomogeneous state formed by isostructural phases of the constituent compositions: the ferromagnetic PdFe alloy undergoing atomic ordering and the antiferromagnetic PdMn intermetallic compound.

Neutron diffraction was used to study structural and magnetic states in quenched and annealed Ni1-xCoxMn alloys. The order-disorder structural transition from the ordered tetragonal to the disordered cubic phase was found to occur at x approximate to 0.3 in quenched alloys and at x approximate to 0.7 in annealed ones. The magnetic structure of theta -NiMn is shown to change upon substitution of Co for Ni in such a manner that the magnetic moments of manganese atoms reorient from the [110] direction in the tetragonal phase toward the [111] direction in the cubic phase and the local moment at manganese atoms decreases from 3.8 to 1.4 mu (B). No magnetic moment is present at nickel and cobalt atoms either in the tetragonal or cubic phases.

Several zirconium phosphate (ZrP) gels of various water contents produced by a sol - gel method were investigated. They were found to be the polymer-class gels using the method of small-angle neutron scattering. X-ray diffraction analysis revealed that their solid-phase framework was formed from branched fragments (layers and blocks) of -ZrP crystal structure. These gels are strongly fluctuating systems when they are on the scale of . Their fluctuation character is shown to be described by two parameters: a correlation radius and a fractal dimension D. It was found that and almost did not depend on the water content and that D increased from to when the water content decreased from 50% to 0% as the gels were dried to a temperature of . Simultaneously, substantial shrinkage of granules, a decrease in porosity and ion-exchange capability, and formation of blocks from -phosphate layers occurred with decrease in the water of the hydrogel as it dried. A probable description of the evolution of the ZrP-gel structure with variation in the water content during drying is suggested on the basis of the data obtained.

Magnetic neutron diffraction measurements have been performed on (Co1−xMgx)O solid solutions with x = 0.1, 0.2, 0.3, 0.43, 0.53, 0.63 and 0.7 at T = 4.2 –300 K. It is shown that the concentration dependence of the average magnetic moment per atom does not obey the condition of simple dilution. The diamagnetic atom results in a local canting of the moments and an additional reduction of the average magnetic moment. One can consider this atom as a source of random magnetic field due to the appearance of a new superexchange interaction between magnetic atoms through the diamagnetic impurity. The sign of this interaction is opposite to the sign of the direct exchange interaction in the magnetic sublattice.

Diffuse neutron scattering measurements were performed on quenched alloys with x = 0.31, 0.36, 0.39, 0.43 and 0.5, which belong to the transition region between ferromagnetism and antiferromagnetism. The nuclear and magnetic cross sections were separated, and Cowley short-range order atomic parameters determined. It was found that the superantiferromagnetic behaviour of these alloys occurred owing to the existence of the antiferromagnetic clusters of the -FeMn type caused by short-range order regions of the CuAu type.

A magnetic phase diagram of the (Ni(1-x)Mg(x))O solid solutions is drawn by the results of elastic magnetic neutron scattering and magnetic measurements. The ranges of homogeneous antiferromagnetism (0 less-than-or-equal-to x less-than-or-equal-to 0.37), tricritical behaviour or frustrated antiferromagnetism (0.37 < x less-than-or-equal-to 0.6), cluster spin glass (0.6 < x less-than-or-equal-to 0.75) and paramagnetic behaviour of the Ni2+ spin moments in the ground state (x greater-than-or-equal-to 0.8) are determined. It is shown that diamagnetic Mg2+ ions serve as a source of a random field inducing an extra diamagnetic moment of value 0.35-mu-B.

The measurement of the neutron small-angle scattering intensity in the range of the scattering vectors q = 0.008-0.5 angstrom-1 is performed for the xerogel samples with the different annealing temperatures. Within the Porod model for the porous structure the interpretation of the maximum in the scattering curve is given and the correlation lengths characterizing the porous structure are determined as well. It is shown that the q --> infinity asymptote of the scattering curves is governed by the power law q(-n) with n = (3.65-4), which is typical for the fractal surface of a solid phase when n < 4. The porous structure parameters determined from SAS, such as, the correlation lengths and specific surface, are compared with the analogous characteristics obtained with another techniques.

AbstractA symmetry analysis of possible magnetic structures in crystals with the space group D is made for the wave vector of star {k12}. This analysis allows deciphering the neutron diffraction data on the character of antiferromagnetic ordering in the AF1 (below T1 = 66 K) and AF2 (below T2 = 99 K) phases. It is shown that the magnetic phase transitions arise mainly from the structural transformations that occur at T1 and T2.