FeRh-based alloys are unique objects, the study of which allows us to identify new features of first-order magnetic phase transitions. Doping of an alloy often leads to significant changes in its magnetic properties. This paper examines the structural, magnetic, transport and caloric properties of iron-rhodium alloys with different cobalt doping with varying cobalt content (0-1.8 at%). Doping the alloy with less than 2 at% cobalt resulted in a decrease in the phase transition temperature by 200 K. Based on the results obtained, a relationship was established between the magnetic properties and the heterogeneity of the elemental composition of the samples. It was also demonstrated that significant changes in the parameters of the magnetic phase transition of the alloy upon alloying are largely determined by the electronic properties. Considering the sensitivity of the alloy properties to the cobalt content, we develop a novel methodology for quantifying local compositional variations using temperature-dependent measurements, demonstrating its superior sensitivity compared to conventional techniques. The strong correlation between magnetocaloric response and cobalt concentration highlights the importance of precise composition control for applications.

The work is devoted to the study of the dependence of the structure, magnetic properties, and functional properties such as shape memory effect (SME) and magneto caloric effect (MCE) of Heusler alloys of the Ni51 – xMn33.4In15.6Vx family on the degree of vanadium doping x. Studies using scanning electron microscope (SEM), differential scanning calorimetry (DSC) and magnetometry revealed in all studied samples of Heusler Ni51 – xMn33.4In15.6Vx alloys the presence of a Curie point type magnetic phase transition (PT) and a metamagnetostructural phase transition (MMSPT), of the first order which is accompanied by a sharp decrease in magnetization in the low-temperature martensitic phase. The temperature of the magnetic PT is weakly dependent on x, the temperature of the MMSPT decreases with increasing x. The temperature of the MMSPT is very sensitive to the magnetic field. For the Ni50Mn33.4In15.6V1 sample, the sensitivity is—5 K/T. Direct measurements of the MCE in alternating magnetic fields of 0.62 and 1.2 T showed the presence of a direct MCE at the point of magnetic PT and an inverse MCE at the point of MMSPT. There is a strong decrease in the MCE with an increase in the frequency of the alternating magnetic field from 1 to 30 Hz both near the magnetic PT and near the MMSPT. Measurements of the dependence of bending deformation on load and temperature have shown that all studied alloys exhibit SME near MMSPT. It can be concluded that due to the combination of high sensitivity of MMSPT to the field and SME, this family of alloys is promising for the creation of magnetically controlled actuators.

Magnetocaloric effect (MCE) and its potential most simple and evident application in magnetic cooling technology represent urgent issues that have been the subject of intensive global investigation over recent decades. The practical use of a material exhibiting a magneto-caloric effect in cooling technology necessitates a cyclic exposure of the material to a magnetic field. It is therefore imperative to undertake a comprehensive study of the magnetocaloric properties of materials subjected to alternating (or cyclic) magnetic fields. This paper presents an overview of the fundamental concepts pertaining to the effect, methodologies for the measurement of MCE in alternating magnetic fields, and the outcomes of MCE studies depending on the frequency of the magnetic field and the duration of exposure of materials to the alternating magnetic field.

The effect of microstructure and the frequency of change in an alternating magnetic field on the adiabatic temperature change ΔTad in manganite Pr0.7Sr0.2Ca0.1MnO3 has been studied. It has been shown that the transformation of specimens from a denser to looser microstructure leads to both a decrease in ΔTad and a stronger frequency dependence of the adiabatic temperature change. For the specimen with an annealing temperature of 1300°C, ΔTad is 0.6 K at a frequency of 1 Hz in a field of 1.2 T to decrease to 0.3 K at 20 Hz (by more than 50

Mono and multicaloric effects in Fe48Rh52 alloy under applied magnetic field, uniaxial tension and their combination were studied by direct method. It was found that for single cases, the inverse caloric effect was observed with delta TAD = -2.9 K (1T) at 330 K in the case of the magnetocaloric effect and delta TAD = -0.5 K (104 MPa) at 328 K in the case of the elastocaloric effect. The combination co-application of the external 1 T magnetic field and a 104 MPa tensile results to the observation of a synergistic effect with delta TAD = -3.4 K at 330 K when a, which exceeds similar values for mono caloric effects. As was shown from comparison of calculation and experiments multicaloric effect it is not a sum of mono caloric effects and several factors as geometry of the sample as well the protocol for applying external fields should be taken into account. It was shown that the distribution of mechanical stresses in the Fe48Rh52 sample with a geometry in the shape of a plate with holes is heterogeneous, which should be taken into account when measuring calorific effects using tension through holes

The results of direct measurements for the adiabatic temperature change ΔTad in the Ni47Mn40Sn13 alloy in cyclic magnetic fields by the magnetic field modulation method are presented. In the temperature dependence of the magnetocaloric effect (MCE), direct (ΔTad > 0) and inverse (ΔTad < 0) MCE are detected. The inverse effect value in a cyclic magnetic field depends on the temperature scanning rate. An increase in the frequency of a cyclic magnetic field with an induction of 1.2 T from 1 to 30 Hz decreases the direct effect value by more than 2 times. In a cyclic magnetic field with an induction of 1.2 T at frequencies f ≥ 1 Hz, complete disappearance (“collapse”) is observed for the inverse magnetocaloric effect, while ΔТad during the one-time actuation of magnetic field is –0.49 K. The dependence of the inverse effect value on the temperature scanning rate, along with its strong frequency dependence, results from both the manifestation of irreversibility in the magnetostructural phase transition due to hysteresis and the presence of phase inhomogeneities influencing the phase transition kinetics.

Materials with a first-order magnetic phase transition demonstrate colossal changes in physical properties near the phase transition temperature. However, the mechanisms of phase transition occurrence are not fully understood. In this work, using the Fe48Rh52 alloy as an example, we study the near-surface magnetic and structural properties of the alloy near the phase transition temperature. Analysis of images obtained using the magnetooptic Kerr effect at different temperatures allowed us to separate the contributions from nucleation and growth of the ferromagnetic phase during the phase transition. Approximation of experimental data by the proposed model allowed us to estimate the surface energy of ferromagnetic clusters with different micromagnetic structures. The work also shows the influence of microscopic features on the formation of macroscopic properties of the alloy.

The ability to control by physical properties of the thermoresponsive polymer of PNIPAM by magnetocaloric effect was demonstrated by in-situ experiments on PNIPAM/FeRh smart composite. The concept of drug release loaded in smart composite by applying of 3 T magnetic field was demonstrated using an example of doxorubicin. Released results of the magnetic field applying the drug were detected using IV-VIS and Raman spectroscopy. In vitro, studies have demonstrated a high degree of PNIPAM/FeRh scaffold biocompatibility for primary mouse embryonic fibroblasts (PMEF) cell culture. PMEFs effectively ad-hered to the PNIPAM/FeRh scaffold surface and showed high metabolic and proliferative activity for 72 h after seeding.

The results of direct measurements for the adiabatic temperature change ∆Tad in a rapidly quenched ribbons Heusler Ni44Co6Mn32Al18 alloy specimen within a temperature range of 100–350 K in a cyclic magnetic field with a strength of 18 kOe and a frequency of 0.2 Hz are presented. It is shown that, in the case of one-time magnetic field actuation, the inverse effect value is –0.25 K at a magnetostructural transition temperature TS. The second and following on/off cycles lead to a decrease in the effect by an order of magnitude to –0.03 K. Such a behavior is associated with the effect of kinetic relaxation in the martensite phase and phase transition irreversibility in the used magnetic fields. Near TC, the stable and direct effect ∆Tad = 0.23 K without degradation signs is observed.

We present the results of direct measurements of the adiabatic temperature change (ΔTad) for the Fe50Rh50 alloy in a cyclic magnetic field (CMF) of 1.2 T. It is shown that increasing the frequency of the CMF from 1 to 30 Hz is accompanied by a shift of the position of temperature dependence ΔTad(T) maximum, Tmax, toward low temperatures. With an increase in the CMF frequency from 1 to 5 Hz, the ΔTmax value decreases by ∼12%. A further increase in frequency leads to stabilization of the effect. In the vicinity of the antiferromagnetic-ferromagnetic phase transition point TC = 370 K, ΔTad exhibits unconventional frequency behavior: while at T well above TC, the value of ΔTad monotonously decreases as frequency increases, at T = 370.4 K; an interval of frequency-independent ΔTad up to 10 Hz is observed, and at 368 K < T < TC, the maximum of ΔTad(f) dependence is found in the interval 1 < f < 10 Hz. Such behavior in the future can be applied in magnetic cooling technology due to large values of ΔTad and the frequency stability of the effect in alternating fields. The specific cooling power reaches giant values of ∼22 W/g at 20 Hz, which is comparable to the values under the same conditions for Gd −21.6 W/g. The unconventional behavior of ΔTad in the CMF is discussed in the context of the role of secondary phase localization, which leads to an enhanced internal local magnetic field and dynamic effects of ΔTad.

Varieties of Mentha piperita L. (peppermint) cultivated at altitudes of 1100 and 1650 m above sea level on identical soils were studied to identify the variability in the accumulation and constituent composition of their essential oils. Essential oils from cultivated samples were obtained by hydrodistillation. The composition of volatile organic substances was determined by GC-MS using a Shimadzu GCMS-QP2010 Plus quadrupole gas chromatograph-mass spectrometer. As a result, up to 58 constituents were identified, including 11 major ones. The quantitative content of the essential oil was found to be highly dependent on the climatic conditions of cultivation, whereas the composition of volatile organic substances varied insignificantly for a certain variety but was highly variable between different varieties.

Some results of studying the temperature dependence of the magnetocaloric effect ΔТad, thermal expansion, and magnetostriction in the Mn1 – хFexAs system (х = 0.003, 0.006) in magnetic fields up to 8 T are presented. It has been shown that an increase in the iron concentration in the Mn1 – хFexAs system leads to the shift of the phase transition temperature towards lower values by 15 K. In a field of 8 T, ΔТad = 8.3 K for Mn0.997Fe0.003As at an initial temperature T0 = 318 K, and ΔТad = 7.7 K for Mn0.994Fe0.006As at T0 = 307 K. The thermal expansion and magnetostriction data show that the magnetostriction decreases with increasing iron concentration, which also leads to a decrease in the magnetocaloric effect.

The influence of as-cast and multiaxial isothermal forged structures on the sensitivity of martensite to the magnetic field and on the magnetocaloric effect in Ni-Mn-Ga-Si alloy has been studied. In the multiaxial isothermal forged state, a "necklace" structure is observed where large grains of 100-200 mu m are encompassed by a layer of fine-grained structure. In this state, the martensitic transformation occurs with a shift towards the lowtemperature region of about 10 K. Characteristic points of the martensitic transformation are evaluated in a magnetic field up to 12 T, revealing a sensitivity value of 0.6 K/T for both as-cast and multiaxial isothermal forged samples. Furthermore, an inverse magnetocaloric effect is identified within the martensitic transformation region for both as-cast and multiaxial isothermal forged samples under weak magnetic fields, up to 0.2 T. This inverse effect disappears at a magnetic field of 1.8 T, leaving only the direct magnetocaloric effect observable. These findings shed light on the intriguing interplay between microstructure, magnetic sensitivity, and magnetocaloric behavior in this Ni-Mn-Ga-Si alloy, offering valuable insights for potential applications in magnetic cooling technologies.

The possibility observation of the electric field controlled multicaloric response through quasi-isostatic compression as a result of the converse piezoelectric effect was demonstrated on the cylindrical type magnetoelectric composite MnAs/PZT. It was shown that an electric voltage of 100 V corresponding to an electric field of E similar to 0.3 kV/mm applied to the walls of the piezoelectric component PZT of the MnAs/PZT composite contributes to an increase in the maximum adiabatic temperature change by 0.2 K in the temperature range of the magnetostructural phase transition of MnAs similar to 317 K at a magnetic field change of 1.8 T. Numerical analysis using the finite element method has shown that an electric field voltage of 100 V is capable of creating a quasi-isostatic mechanical stress in the region inside a cylindrical PZT tube of similar to 3 MPa. Moreover, in the region of weak pressures up to 10 MPa, the contribution to the total adiabatic temperature change from piezo-mechanical compression linearly depends on the electrical voltage that can be used for control by magnetic and caloric properties of multicaloric materials. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

It is shown that the phase shift between an applied weak alternating magnetic field and the magnetocaloric response signal of the magnetic material is drastically sensitive to the order of phase transition. Namely, at the second-order phase transition, the phase shift does not depend on the magnetic field magnitude, while in the first-order phase transition this one depends significantly on the field strength. We have shown that this effect follows from the general critical dynamics theory.

This paper presents for the first time the results of studying the total content of antioxidants in the seeds of Morus L. The composition of fatty and steric acids of the seeds of mulberry fruits Morus L. was also studied: polymorphic species Morus alba (white-fruited, pink-fruited, black-fruited) and Morus nigra (Khartut variety). As a result of the studies, 12 fatty acids were identified. The main ones were linoleic acid, palmitic oleic acid, and stearic acid. The predominant fatty acid in all samples was linoleic, which varied from 67.5 to 79.0%. 15 sterols were found, among which β-Sitosterol accounts for about 90%. Determination of the total antioxidant content of Morus alba seeds (white-fruited, pink-fruited, black-fruited forms) and Morus nigra (Khartut variety) revealed the accumulation of antioxidants in all samples. The highest total content of antioxidants was observed in Morus nigra (4.40 mg/g) and the white-fruited form of Morus alba (5.56 mg/g).

First-principles studies on phase stability and resistance with respect to the segregation of austenitic and martensitic phases of Ni2 – xCoxMn1 + yZ1 – y Heusler alloys (x = 0, 0.25, 0.5 and y = 0, 0.25, 0.5, 0.75; Z = Ga, In, Sb, Sn) with different types of magnetic ordering. Among all the considered compounds, the stability has been demonstrated only by the Ni1.5Co0.5MnGa and Ni2MnGa alloys in the cubic and tetragonal structures having a ferromagnetic ordering, respectively, as well as by Ni2Mn2 in the tetragonal structure with a staggered and layer-by-layer AFM ordering. For the case of these compositions, the presence of zero energy of the convex hull, as well as the absence of reactions with positive decomposition energy has been shown. The remaining compounds appear to be metastable, both owing to the presence of stable reactions with negative decomposition energy, and decomposition reactions with positive decomposition energy. The number of decomposition reactions exhibits an increase with increasing chemical disorder, i.e., with deviations from stoichiometry.

The magnetization and magnetostriction of polycrystalline LaFe11.2 – хMnxCo0.7Si1.1 alloys (x = 0.1, 0.2, 0.3) were measured in pulsed magnetic fields up to 180 kOe in the temperature region of 80–270 K. The substitution of Fe atoms by Mn atoms shifts ТС towards lower temperatures and has no effect on the saturation magnetization. The observed magnetization–field dependence M(H) near ТС is typical of the second-order phase transitions, whereas the magnetization–temperature dependence M(Т) above ТС in strong magnetic fields indicates the occurrence of a first-order phase transition. The magnetovolume effect ∆V/V attains 0.81

The results of a study of the resistivity, thermal conductivity, thermoelectric power, and thermal expansion of a polycrystalline Ni47Mn40Sn13 Heusler alloy as a function of temperature (80-350 K) and magnetic field (0-8 T) are presented. In addition, ab initio calculations of the structural, electronic magnetic and thermal properties of Ni-Mn-Sn alloy are performed. It is shown that the sensitivity of the magnetostructural phase transition (MSPT) to a magnetic field is Delta T/Delta H approximate to 2 K/T. The temperature dependence of the thermoelectric power near the temperature of the magnetostructural phase transition has a minimum, which is due to a competition between the contributions of electrons and holes to the thermoelectric power. In the region of the martensitic transition, a jump-like increase in thermal conductivity Delta kappa approximate to 4.2 W/mxK was detected, which is associated with both an increase in the electronic component due to an increase in the mobility of charge carriers, and an increase in the free path of phonons as a result of narrowing of the phonon relaxation channel upon transition to a less defective austenitic phase. The ab initio calculations reproduce well a jump-like behavior in the electronic and phonons components of thermal conductivity, providing Delta kappa of 4.63 W/mxK for electron-doped compound. It is shown that the martensitic transformation between the austenitic and martensitic phases is accompanied by a slight change in the carrier concentration, which is about 3 %. This result confirms the experimental suggestion about the weak change in the charge carriers at the martensitic transformation. The martensite-austenite phase transition is accompanied by a sharp increase in the linear dimensions of the sample Delta l/l(0)approximate to 1.5x10(-3). A direct relationship was found between Delta rho/Delta rho(0) and magnetostriction near the MSPT temperature in a magnetic field of 1.8 T.

The purpose of the study is to study the component composition of the essential oil in the aerial part of the endemic Krasnodar specimen Thymus pulchellus S. A. Mey., transplanted to the Tsudakhar experimental base of the Mountain Botanical Garden of the Dagestan Federal Research Center of the Russian Academy of Sciences (CEB, 1000 m above sea level, Dagestan, Russia ) to search for plants with a high yield of essential oil with a maximum content of valuable biologically active components and expand the growing area of this type of thyme. Material and methods. The aerial part of the Thymus pulchellus introduced at the CEB was collected in the flowering phase. The essential oil was obtained by hydrodistillation (Clevenger method) for 2 hours from dry raw materials prepared by conventional methods. Component qualitative and quantitative analysis of the isolated essential oil samples was carried out by chromatography-mass spectrometry on a Shimadzu GCMSQP2010plus on a Supelco SLB TM-5 ms column (30 m × 0.25 mm × 0.25 μm) in split mode. Results. The EF yield was 0.26% in terms of air-dry raw materials. Using chromatography-mass spectrometry, 56 components were isolated from EF samples, of which 97.67% of compounds were identified. Conclusions. For the first time, data are presented on the study of the composition of the essential oil from the aerial part of the introduced Dagestan sample of Thymus pulcellus. The resulting essential oil consists mainly of the sesquiterpene fraction (84.12%). Compared to other species, the essential oil of the studied pretty thyme showed a completely different set of main components, among which the main ones are limonene, γ-cadinene, α-muurolol, epicubenol, which allows us to assert the isolation of this species. The results obtained allow us to characterize the essential oil of Thymus pulchellus as a source of valuable components, and the plant itself as a promising medicinal raw material.