The antiferromagnetic L10 B-NiMn compound has a Neel temperature of up to 800 degrees C and is capable of providing the exchange bias effect in multilayered structures with adjacent ferromagnetic layers, such as Fe20Ni80, up to 350 degrees C. The value of the exchange bias field can be non-decreasing up to 150 degrees C, making Ni-Mn a compelling choice for applied devices based on the exchange bias effect. In this work we study the structural transformations occurring in magnetron-sputtered Ni-Mn/Fe20Ni80 films that first lead to the emergence of exchange bias in these structures, and then to its disappearance. Employing in situ X-ray diffractometry and vibrating-sample magnetometry we observe how under annealing the phases of Ni-Mn follow Ostwald's rule of stages on their way to form the equilibrium B-NiMn. Our findings suggest that at temperatures of around 350 degrees C diffusion of iron from the ferromagnetic layer causes decomposition of B-NiMn, ultimately resulting in the irreversible disappearance of exchange bias. Our results reveal the role of adjacent Fe20Ni80 layers in the transformations, and how crystal texture in the Ni-Mn layer affects exchange bias. The results of our work not only clarify the fundamental mechanisms but also provide valuable insights for engineering and utilizing of applied devices with Ni-Mn, making it of interest to material scientists and engineers of different specializations.

Thin-sheet rolled low-carbon manganese steel 09G2S with a thickness of 0.8 mm which has strong property anisotropy due to texture and residual stresses, was experimentally studied using SH-wave with horizontal polarization and zero-order symmetric Lamb wave mode. The velocities of elastic wave propagation along the sheet were analyzed as their direction and polarization varied relative to the rolling direction in the range of angles from 0° to 180°. The excitation and reception of normal waves in the sheet were carried out by piezoelectric transducers with dry point contact, providing tangential force application. The results of the research on the anisotropy of acoustic properties, X-ray structural analysis of residual stresses and inverse pole figures, and metallographic studies were obtained.

The key elements of the compact accelerator-driving neutron source (CANS) dedicated to academic research and industrial applications (DARIA) have been developed. A pulsed proton linear accelerator with an energy of 13 MeV, a current of 100 mA, a pulse length of 100 μs, and a repetition rate of 100 pulses/s is under development for the DARIA CANS. An improved version of the GISMO ion source has been developed to generate the beam. The parameters of the accelerator line consisting of the RF quadrupole (RFQ) linac and the drift tube linac (DTL) have been determined by numerical simulation. The parameters and model of a hybrid magnetic lens for beam focusing are presented. A Faraday cup for diagnosing a high-intensity beam has been manufactured and tested. The developed prototypes of the target assembly based on beryllium and mesitylene moderator have confirmed the correctness of the selected engineering solutions. The physical parameters of the neutron-guiding systems have been determined in terms of the maximum luminosity of the device at a good instrumental resolution.

The article presents the results of a systematic study of the crystalline structure, microstructure, and hysteresis properties of (Cr 80 Mn 20 )/Fe bilayers, deposited on buffer coatings of various metals (Cr, Fe, W, Ta). It has been established that depending on the composition of the buffer coating and the thickness of the Cr-Mn layer, the latter develops body-centered cubic structure with either the (110) or (200) texture, or none. It is shown that the Cr-Mn layer is a source of increased coercivity in the adjacent Fe layer and when is in a certain structural state and has a relatively large thickness (100 nm) induces exchange bias in the Fe layer. The regularities obtained are interpreted in terms of the antiferromagnetic ordering of Cr-Mn and its relatively weak magnetic anisotropy Keywords: antiferromagnetics, ferromagnetic, bilayers, thickness, composition, temperature, texture, coercivity, exchange bias.

We have shown the feasibility of detecting gamma quanta in a neutron experiment in the mode of resonantly enhanced standing waves (RESW) from a 1 nm thick gadolinium film placed in a resonator structure consisting of a 50 nm niobium layer on a sapphire substrate and coated with a 10 nm tantalum-copper film alloy. The mass of gadolinium used in the experiment was 2 μg, which is 25 times less than that in the experiment by H. Zhang et al. (H. Zhang et al., Phys. Rev. Lett. 72, 3044 (1994)). Quantitative calculations show that the experimental conditions make it possible to detect a gamma signal at waveguide resonance from a gadolinium sample weighing 40 nanograms. Thus, RESW gamma spectrometry is a powerful method for characterizing heterostructures with ultrathin gadolinium layers. In particular, it can be used to study the kinetics of interaction of hydrogen with nanometer films in which a thin layer of gadolinium is used as a label layer.

In this paper we study the formation of the antiferromagnetic Cr -Mn alloys with body-centered cubic crystal structure, and their capability to act as a pinning layer for the exchange bias effect in magnetron-sputtered polycrystalline films. By means of X-ray diffractometry, executed in different geometries, we perform a thorough analysis of Ta/Cr-Mn/Ta films, which results in the construction of a room-temperature phase diagram of Cr -Mn. These results combined with magnetic measurements of films with adjacent antiferromagnetic Cr -Mn and ferromagnetic Fe 20 Ni 80 layers allow us to establish the conditions for the observation of the exchange bias effect, the maximum blocking temperature T b of which can be as high as 540 K. Employing a specialized measurement protocol, we estimate the effective anisotropy constant K eff , whose values help to explain thickness dependence of the exchange bias field in structures with a Cr -Mn pinning layer.

Abstract—The study is related to the investigation of hysteretic and magnetostrictive properties of single-layer Fe10Ni90 films and nano-structured [Fe10Ni90/Cu]p/Fe10Ni90 films, in which magnetostrictive layers are separated with a nonmagnetic interlayer. The magnetostriction effect is shown to depend on the total layer thickness; in this case, the magnetostriction of the [Fe10Ni90/Cu]p/Fe10Ni90 film structures was found to be higher than that of the single-layer Fe10Ni90 films. The observed peculiarity is associated with weakening the fixing effect of a substrate.

X-ray and magnetometry methods are used to show that, during magnetron sputtering of Dy/Co periodic multilayer systems, the DyCo2 and DyCo3 intermetallics form. The main reason for the phase formation of various intermetallics is the structural state of buffer layer, namely, its crystalline and amorphous state in the case of crystalline and glass substrate, respectively.

We present in this paper the experimental results of magnetothermal properties in Dy films and their comparison with the theoretical modeling of the same data. We consider the temperature interval between 80 and 200K, where Dy is ferromagnetic in low-temperature regions and helimagnetic for high temperatures. Our findings show that due to different phases in the considered temperature interval, the Dy induces thermal hysteresis in specific applied fields. We found that the ferromagnetic phase is favored in the heating process, and in the cooling process, the helimagnetic phase is favored.

The application of the method of phase-amplitude functions to the calculation of neutron-transmission processes in layered media containing highly absorbent elements is described. This method allows us to simultaneously calculate the reflection, transmission and absorption coefficients for neutrons. It requires less computing resources than other algorithms. A generalization of the method to matrix equations used in polarized neutron reflectometry is also presented. Examples of calculations of various characteristics of neutron transmission for layered resonator-type systems with a potential well are given.

Polarized neutron reflectometry is used to study Dy/Gd superlattices with different ratios of Dy- and Gd-layer thicknesses: 1 : 1, 2 : 1, and 3 : 1. It is experimentally shown that the formation of helicoidal magnetic ordering in Dy layers with a period incommensurate with that of the superlattice manifests itself in the appearance of a magnetic-superlattice reflection, which is forbidden due to equality of the thicknesses of alternating Dy and Gd layers with a ratio of 1 : 1. Otherwise, the formation of helicoidal magnetic ordering has little effect on the shape of the neutron-reflectometry curves. Thus, optimization of the structure of rare-earth superlattices for the neutron-reflectometry experiment makes it possible to detect helicoidal magnetic ordering in superlattices with a period incommensurate with the structural superlattice ordering.

This paper presents an approach to solving the phase problem in neutron reflectometry (including polarized neutron reflectometry) based on the effect of the resonant interaction of nuclei of gadolinium isotopes 155Gd and 157Gd with thermal neutrons. This effect is used to implement the reference-layer method, which allows one, based on the results of three experiments, to calculate the complex reflection coefficient of the sample under study. Knowing the complex reflection coefficient makes possible model-independent analysis of the interaction potential, both nuclear and magnetic. The main application of this approach is the study of the structure of layers and interfaces, as well as determination of the magnetic state of multilayer metal nanoheterostructures. The theoretical basis of this method is given, which consists in deposition onto the studied sample of a gadolinium layer with known parameters, one of which can be varied in a controlled manner. The scheme of the experiment is described in detail using model numerical calculations. An experimental result is given for a simple single-layer niobium sample, for which the modulus and phase of the reflection coefficient are calculated. Promising directions for improving the method and possible directions for further work are proposed. Expectations for the characteristics of a compact neutron source, which are necessary for optimal implementation of the proposed method, are formulated.

The article presents the results of a systematic study of the crystalline structure, microstructure, and hysteresis properties of (Cr80Mn20)/Fe bilayers, deposited on buffer coatings of various metals (Cr, Fe, W, Ta). It has been established that depending on the composition of the buffer coating and the thickness of the Cr-Mn layer, the latter develops body-centered cubic structure with either the (110) or (200) texture, or none. It is shown that the Cr-Mn layer is a source of increased coercivity in the adjacent Fe layer and when is in a certain structural state and has a relatively large thickness (100 nm) induces exchange bias in the Fe layer. The regularities obtained are interpreted in terms of the antiferromagnetic ordering of Cr-Mn and its relatively weak magnetic anisotropy

The influence of a number of physical factors on the structural and hysteresis properties of multilayer films (Cr-Mn)/Fe Ni has been studied. By indirect signs, the presence of antiferromagnetism in Cr-Mn layers with a Mn content in the range of 20-40 at.% has been established. It is shown that in such structures, the exchange bias effect can be observed, but only when the thickness of the antiferromagnetic layer is greater than 40 nm. The initial reason for the low "fixing" properties of the Cr-Mn layer is its weak magnetic anisotropy, which is superimposed with instability in the reproduction of the micro-structure. The use of substrate heating during film deposition increased the reproducibility of microstructure parameters and hysteresis characteristics but led to a weakening of the exchange bias effect, apparently due to changes in the structure and composition of the interlayer interface.

This paper presents a detailed study of the hysteresis properties of film structures based on bilayers of the Cr-Mn/Fe type. The temperature dependences of several parameters of the hysteresis loops of the Fe layers are determined for films varying in the composition and thickness of the Cr-Mn layer, as well as in the structure of buffer coatings. The compositional and temperature intervals of the existence of the antiferromagnetic ordering in the Cr-Mn layer and the related features of the temperature changes in the coercive force, its anisotropy in the plane of the films and the exchange bias field are established. The causal analysis of the established regularities is performed. Keywords: antiferromagnet, ferromagnet, bilayers, thickness, composition, temperature, texture, coercive force, exchange bias.

Abstract—Structural studies of multilayer magnetic nanostructures formed by alternating layers of transition (Fe) and rare earth (Gd) metals placed in a hydrogen atmosphere at a temperature of 100°C have been carried out. When hydrogen is absorbed by rare earth metals, crystalline phases GdHx arise (form), the microstructural features of which were studied by X-ray diagnostics and electron microscopy.

Proximity effects in structures with helimagnetic ordering are investigated. Structures with sharp boundaries were prepared by magnetron sputtering. Results indicating a change in the magnetic state of a helimagnet under the influence of superconductivity were obtained by polarized neutron reflectometry. A new type of structure with alternating layers of a superconductor and a rare-earth helimagnet is proposed for studying magnetic proximity effects. The results of studies using X-ray methods and atomic force microscopy demonstrate the high quality of the obtained structures.

Aspects of the experimental implementation of the small-angle neutron scattering (SANS) method on a compact neutron source are considered. A scientific justification of the demand for this type of installation is formulated. A scheme for implementing the SANS method on a pulsed neutron source is proposed, which ensures the high efficiency of using a neutron beam by limiting the operating wavelength range, and, as a result, maximizing the frequency and time-averaged power/intensity of the source. The physical parameters of the key elements of the installation, such as the cold neutron moderator, the beam-chopper cascade, the collimation system, the sample unit and the wide-aperture position-sensitive detector, are described. It is shown that the small-angle scattering method can be implemented on a university-type pulsed neutron source.

This paper presents a detailed study of the hysteresis properties of film structures based on bilayers of the (Cr-Mn)/Fe type. The temperature dependences of several parameters of the hysteresis loops of the Fe layers are determined for films varying in the composition and thickness of the Cr-Mn layer, as well as in the structure of buffer coatings. The compositional and temperature intervals of the existence of the antiferromagnetic ordering in the Cr-Mn layer and the related features of the temperature changes in the coercive force, its anisotropy in the plane of the films and the exchange bias field are established. The causal analysis of the established regularities is performed.

Structural studies of multilayer magnetic nanostructures formed by alternating layers of transition (Fe) and rare-earth (Gd) metals, which are placed into a hydrogen atmosphere at 100°C, are performed. The hydrogen absorption of rare-earth metals results in the formation of GdH x crystalline phases, the microstructural peculiarities of which are studied by X-ray diagnostics techniques and electron microscopy.