The results of experimental verification of the feasibility of enhancing the efficiency of neutron-beam polarizers based on magnetized supermirrors are presented. The idea is to use both spin components of a neutron ensemble in a beam. The positive component is reflected from one magnetized mirror, and the negative component, which passes through it, is rotated by 180° and reflected from another mirror. Both beams were detected by a single detector. With the coefficients of reflection of spin components from the mirrors and the efficiency of rotation of the negative component factored in, an approximately twofold enhancement of the neutron intensity was obtained at an average polarization of ~66%. A monochromatic neutron beam was used in these experiments.

The results of experimental verification of the possibility of increasing the neutron beams luminosity of polarizing devices based on magnetized supermirrors are presented. The essence of the experiment is to use both components of the neutron spins in the beam. The positive component is reflected from one magnetized mirror, and the passing mirror opposite component after turning 180 degree is reflected from another similar mirror. Both beams were recorded with one detector. Taking into account the reflection coefficients of the components by the mirrors and the efficiency of the rotation of the opposite component, an increase in the neutron intensity was obtained approximately twice with an average polarization of about 66%. The experiments were performed on a monochromatic neutron beam.

The main directions of development of the project on the modernization and improvement of the REVERANS reflectometer, which is proposed to be installed at the PIK reactor (REVERANS-2), are described. They include the substitution of magnetic materials in instrument construction and the replacement of the autonomous table for samples; the equipment of the instrument with a polarimeter to measure the polarization components of incident and reflected neutron beams; and replacement of the electronics and mechanisms for moving the platforms. The REVERANS-2 parameters expected after modernization are given.

A device that forms a vertically diverging neutron beam is described. The device allows scanning at the angle of incidence of neutrons on a fluid surface in a reflectometer with a vertical scattering plane. Computer simulation of the former is carried out, and the beam characteristics (horizontal and vertical divergences and the neutron energy spectrum) are obtained. These characteristics are compared with experimental data. Three units are the main advantages of the former: specially fabricated input and output collimators and neutron filters. The reasons for differences in the experimental and simulated data are discussed.

The possibility of application of a foil with an electric current to modulate a beam of polarized neutrons to measure their spectrum is discussed. The experimental results of this application are presented for the measurement of spectra with various wavelength distributions of neutrons. The advantages of this chopper are noted.

The behavior of a magnetic flux in a ceramic high-temperature superconductor with rotation of a magnetic field through a specified angle has been investigated using polarized neutrons. Two models of penetration of a weak magnetic field into a granular superconductor have been discussed. Based on the obtained distributions of the rotation angle and the magnitude of the magnetic field inside the sample, the choice is made in favor of one of these models.

High concentration of two types of P donors up to 1017 cm-3 in SiC enriched with 30Si after neutron transmutation doping (NTD) has been achieved. It was established that annealing at sufficiently low temperature of 1300oC, that is 500-600°C lower compared with annealing of NTD SiC with natural isotope composition, gives rise to the EPR signal of shallow P donors, labeled sPc1, sPc2 and sPh. The correlated changes of the EPR spectra of the three sP centres in all the experiments and the qualitative similarities with spectra of shallow N donors prove that these centres have shallow donor levels and a similar electronic structure and belong to different lattice sites. The annealing at 1700°C results in a transformation of one type of P donors (sPc1, sPc2 and sPh) into another type having low temperature EPR spectra labeled dP.

The Pd1−x Fe x )0.95Mn0.05 alloy with random competing interaction was studied by measuring the muon spin relaxation in an external transverse magnetic field and in a zero magnetic field. Using the measured temperature dependence of the dynamic relaxation rate λ and the characteristics of the distribution of local static fields, the phase states of the sample under study are refined. In particular, it is shown that the ferromagnetic and spin-glass states coexist simultaneously in the sample below 25 K. Combined studies of the sample using the μSR and neutron depolarization methods made it possible to determine the size of magnetic inhomogeneities to be 2–6 μm in the temperature range 5–40 K.

To study the free surface of liquids, a Reverans reflectometer with a vertical neutron scattering plane has been designed and is fabricated at Petersburg Nuclear Physics Institute. This reflectometer is intended to investigate surfaces and interfaces in liquid magnetic or nonmagnetic systems. The principles of reflectometer operation are described. The general view of the reflectometer with ready units is presented and its main technical parameters are given. The results of preliminary tests are reported.

Investigation of the magnetic structure of the diluted (Pd 0.984 Fe 0.016 ) 0.95 Mn 0.05 alloy at meso-and nanoscale levels by means of two techniques of small-angle polarized-neutron scattering (within a direct beam and beyond it) has been performed in the temperature range 10< T <60 K. The dependences of the neutron beam depolarization, the polarization rotation angle, and the polarization-dependent magnetic scattering cross section on a weak (0< H <40 A/cm) external magnetic field have been studied. A simple model of neutron beam depolarization by a sample with uniaxial magnetic anisotropy was used to analyze the results obtained. The experiment on polarized-neutron scattering in the so-called direct geometry showed the existence of a polarization-dependent scattering cross section. This scattering has left-right asymmetry and depends on temperature. Comparison of these results with the depolarization data leads to a conclusion about the existence of static chiral fluctuations in large-scale inhomogeneities.

Phosphorus-doped silicon 30Si monoisotope samples with a highly homogeneous impurity distribution at a concentration of 5 × 1016 cm−3 were obtained for the first time by means of neutron transmutation doping.

Electron spin resonance (ESR) is used to study the neutron transmutation doping of silicon crystals enriched with 30Si isotope: phosphorus donors and radiation defects produced in the course of transmutational doping are observed. The ESR signals related to the phosphorus uncontrolled impurity in 30Si before transmutational doping (the P concentration is ∼1015 cm−3) and phosphorus introduced by neutron irradiation with doses ∼1 × 1019 cm−2 and ∼1 × 1020 cm−2 (the P concentrations are ∼5 × 1016 and ∼7 × 1017 cm−3, respectively) are studied. As a result of drastic narrowing of the phosphorus ESR lines in 30Si, the intensity of lines increased appreciably, which made it possible to measure the phosphorus concentration in the samples with a small volume (down to 10−6 mm−3). The methods for determining the concentration of P donors from hyperfine structure in the ESR spectra of isolated P atoms, exchange-related pairs, and clusters that consist of three, four, and more P donors are developed. In the region of high concentrations of P donors, in which case the hyperfine structure disappears, the concentration of P donors was estimated from the exchange-narrowed ESR line.

In magnetic colloids of sufficiently high particle concentration, frustration of dipolar interactions could arise as found in spin-glass systems. To understand this situation, a ferrofluid consisting of magnetite particles was frozen in either a horizontal or a vertical field and then 3D neutron-polarisation analysis was performed around the hysteresis loop in both field configurations. The same was done in the fluid state. A comparison of the data leads to the conclusion that frustration plays a key role in the self-organisation of nanoparticles in a frozen magnetic colloid.

3-D neutron depolarisation data were taken from ferrofluids of several concentrations along magnetic loops with the field both parallel and perpendicular to the neutron direction. The data taken at a concentration of 10 vol % of Fe3O4 indicate a strong dependence of the organisation of the ferrofluid particles on the magnetic history over several cycles of the field.

. In PdFeMn alloys with different Fe-atom concentrations, the behaviour of both mean magnetization and neutron depolarization in the magnetization/demagnetization process was observed by three-dimensional analysis of neutron-beam polarization. Both magnetization and depolarization have a hysteresis loop for the same values of an applied field. Depolarization loops are sharply distinguished for different alloys. This gives evidence of different magnetic mesostructures in these alloys.