Decrease In Cell Volume Research Articles

Elevation of Intracellular Na+ Contributes to Expression of Early Response Genes Triggered by Endothelial Cell Shrinkage.

Prolonged hyperosmotic shrinkage evokes expression of osmoprotective genes via nuclear factor NFAT5-mediated pathway and activates Na+ influx via hypertonicity-induced cation channels (HICC). In human umbilical vein endothelial cells (HUVEC) elevation of intracellular sodium concentration ([Na+]i) triggers transcription of dozens of early response genes (ERG). This study examined the role of monovalent cations in the expression of Na+i-sensitive ERGs in iso- and hyperosmotically shrunken HUVEC. Cell volume was measured by 3D reconstruction of cell shape and as 14C-urea available space. Intracellular Na+ and K+ content was measured by flame atomic absorption spectrometry. ERG transcription was estimated by RT-PCR. Elevation of medium osmolality by 150 mM mannitol or cell transfer from hypo- to isosmotic medium decreased cell volume by 40-50%. Hyperosmotic medium increased [Na+]i by 2-fold whereas isosmotic shrinkage had no impact on this parameter. Hyperosmotic but not isosmotic shrinkage increased up-to 5-fold the content of EGR1, FOS, ATF3, ZFP36 and JUN mRNAs. Expression of these ERGs triggered by hyperosmotic shrinkage and Na+,K+-ATPase inhibition by 0.1 µM ouabain exhibited positive correlation (R2=0.9383, p=0.0005). Isosmotic substitution of NaCl by N-methyl-D-glucamine abolished an increment of [Na+]i and ERG expression triggered by mannitol addition. Augmented expression of ERGs in hyperosmotically shrunken HUVEC is mediated by elevation of [Na+]i.

Ultrahigh-pressure isostructural electronic transitions in hydrogen.

High-pressure transitions are thought to modify hydrogen molecules to a molecular metallic solid and finally to an atomic metal1, which is predicted to have exotic physical properties and the topology of a two-component (electron and proton) superconducting superfluid condensate2,3. Therefore, understanding such transitions remains an important objective in condensed matter physics4,5. However, measurements of the crystal structure of solid hydrogen, which provides crucial information about the metallization of hydrogen under compression, are lacking for most high-pressure phases, owing to the considerable technical challenges involved in X-ray and neutron diffraction measurements under extreme conditions. Here we present a single-crystal X-ray diffraction study of solid hydrogen at pressures of up to 254 gigapascals that reveals the crystallographic nature of the transitions from phase I to phases III and IV. Under compression, hydrogen molecules remain in the hexagonal close-packed (hcp) crystal lattice structure, accompanied by a monotonic increase in anisotropy. In addition, the pressure-dependent decrease of the unit cell volume exhibits a slope change when entering phase IV, suggesting a second-order isostructural phase transition. Our results indicate that the precursor to the exotic two-component atomic hydrogen may consist of electronic transitions caused by a highly distorted hcp Brillouin zone and molecular-symmetry breaking.

Effect of Ni doping on the microstructure and magnetic properties of Fe–Ga ribbons

A set of Ni doping Fe–Ga ribbons were fabricated using melt spinning method. The microstructure was studied using extended X-ray absorption fine structure spectroscopy (EXAFS), high resolution X-ray diffraction (HRXRD) and metallurgical microscope. The results of microstructure indicated that as Ni concentration increased, the lattice matrix transformed from body-centred cubic (bcc) to face-centred cubic (fcc), with the decrease of unit cell volume and the emergence of little amount B2 and E21 phase. The result of magnetic and magnetostrictive properties showed that the saturation magnetization decreased with Ni doping. (110) texture in studied ribbons resulted in low saturation magnetic field and high saturation magnetostrction. In addition, small amount of precipitated phase E21 improved the magnetostricion of FeNiGa ribbons.

MORPHOLOGICAL AND MORPHOMETRICAL FEATURES IN DUNALIELLA SALINA (CHLAMYDOMONADALES, DUNALIELLACEAE) DURING THE TWO-PHASE CULTIVATION MODE

The paper presents studies of morphological and morphometrical characteristics of green halophilic carotenogenic microalga Dunaliella salina (Dunal) Teodoresco, 1905, from the south-west region of Crimean Peninsula. D. salina was cultivated in two-phase mode under conditions of natural illumination at the premises of A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS (IBSS), Sevastopol, Russia. The maximum D. salina cell density was 1.69·106 cell/ml in the “green” phase and 0.84·106 cell/ml in the “red” growth phase. The maximum productivity by cell number reached 0.15 ∙ 106 cell/(ml·day)in the “green” phase while it was lower by 73% in the “red” phase (0.04∙106 cell/(ml·day). Along with the maximum productivity, linear growth stage in the first phase was characterized by a maximum fraction of small (up to 500 μm3 in volume) cells (about 15-29%) and a decrease in cell volume by 40-45% as compared with initial value. The mean of D. salina cell volume in the “red” phase was 30% higher than in the “green” phase. At the same time, the large cell fraction in the “red” phase was consistently high (15-35%). The patterns of change in morphological and morphometrical cell parameters were in accordance to stage and conditions of growth. Thus, cell elongation was noted in the stage of linear growth, while under unfavorable conditions at growth-declining stage cells became more round-shaped, with orange and tile-red coloration and granulation of cell content. It was shown that morphological and morphometric cell parameters can serve as additional criteria for assessment of physiological condition in D. salina culture. The experiment demonstrated the prospects for two-stage D. salina cultivation in Crimea.

Hemoglobin deoxygenation and methemoglobinemia prevent regulatory volume decrease in crucian carp (Carassius carassius) red blood cells.

Fish red blood cells (RBCs) exhibit an oxygen-dependent regulatory volume decrease (RVD) in hypoosmotic environment. In higher vertebrates, membrane-associated hemoglobin is involved in the regulation of osmotic ion movements across the cellular membrane. However, whether the hemoglobin conformational state plays a role in the regulation of osmotic responses in fish red blood cells is still not fully understood. We found that changes in hemoglobin conformation influence the pattern of the regulatory volume decrease in Carassius carassius red blood cells. In oxygenated cells (96.4 ± 3.7% oxygenated hemoglobin), the volume recovery was completed within 125min. Deoxygenation of hemoglobin (96.5 ± 2.7% of deoxygenated hemoglobin) inhibited the volume decrease in hyposmotically swollen red blood cells. Reoxygenation restored regulatory volume decrease in cells within 5min. Induced methemoglobinemia (48.4 ± 1.8% of methemoglobin and 41.3 ± 2.3% of deoxygenated hemoglobin) blocked the process of volume recovery and significantly decreased osmotic stability of red blood cells.

Effect of low temperature on the regulation of cell volume after hypotonic shock in gastric cancer cells.

Although peritoneal lavage with distilled water performed after surgery prevents peritoneal seeding, cancer cells may avoid rupture under mild hypotonicity through regulatory volume decrease(RVD), which is the homeostatic regulation of ion and water transport. The aim of the present study was to investigate the effect of low temperature on cell volume and cell death under hypoosmolal conditions and determine the underlying molecular mechanisms in gastric cancer (GC). Three human GC cell lines (NUGC4, KATO‑III and MKN45) were exposed to hypotonic solutions, and the effects of low temperature on cell volume and viability were examined. Low temperature‑induced changes in membrane transporters were evaluated, and knockdown and overexpression experiments were conducted to determine their effects on cell volume during hypotonic stimulation. Low temperature (24˚C) during hypotonic stimulation inhibited RVD and enhanced the cytocidal effects on GC cells. The expression of leucine‑rich repeat containing proteinA (LRRC8A), a component of a Cl‑ channel, was decreased, and aquaporin5 (AQP5) expression was increased at low temperatures. LRRC8A knockdown markedly slowed the decrease in cell volume following cell swelling by hypotonic shock. AQP5 overexpression enhanced initial cell swelling after hypotonic shock and increased the final cell volume. These results suggest that a hypotonic solution at low temperature increased initial water influx via activation of AQP5 and decreased Cl‑ efflux via inhibition of LRRC8A. Therefore, low temperature enhanced the hypotonicity‑induced cytocidal effects on GC cells, and these results may contribute to the development of a novel lavage method effective in reducing peritoneal recurrence in GC.

Studies of the fergusonite to scheelite phase transition in LnNbO4 orthoniobates

Synchrotron X-ray powder diffraction methods have been used to obtain accurate structures of the lanthanoid orthoniobates, LnNbO4 at room temperature. The observed decrease in the unit cell volume in going from Ln = La to Lu correlates with a decrease in the volume of the LnO8 polyhedra due to the changing size of the Ln3+ cation. In all cases the Nb is in a highly distorted six-coordinate geometry with two long, ~2.5 Å, and four short ~1.9 Å Nb–O distances. The importance of the long Nb–O bonds is evident from Bond Valence Sum Calculations. Variable temperature structural studies of three examples, Ln = La, Sm and Gd, showed each transformed to a high temperature tetragonal scheelite type structure in space group I41/a. In the high temperature structure the Nb are tetrahedrally coordinated and it appears that monoclinic – tetragonal transition is best described as a reconstructive transition in which the long Nb–O(1) bond is broken upon heating.

Real-Time Monitoring of the Regulatory Volume Decrease of Cancer Cells: A Model for the Evaluation of Cell Migration

Cell migration plays a vital role in carcinoma invasion and metastasis. Cell regulatory volume decrease (RVD), a mechanism of adjusting cell volume, is a basic physiological function of cells, which is closely related to cell migration. In this work, a quartz crystal microbalance (QCM) cytosensor was first developed for real-time monitoring of cell RVD to evaluate the migration of human breast cancer cells. While stimulating the immobilized cells on the chip with hypotonic solutions, the temporal dynamics of RVD can be tracked by QCM sensor via analyzing frequency shifts during the cell swelling and shrinkage. The results showed that, due to the difference in cell migration capability, the level of RVD for MCF-7 cells and MDA-MB-231 cells was 32.8 ± 2.9% and 49.7 ± 4.2% ( n = 3), respectively. Furthermore, tamoxifen, a chloride channel blocker, was used to suppress cell RVD, indicating concentration dependence and inhibition difference in both types of cells. Combining QCM measurement with cell migration assay, the results showed that the blockage of RVD was positively correlated to the inhibition of cell migration with tamoxifen concentration ranging from 5 to 60 μM, which revealed the relation between cell RVD and cell migration. The study provided a noninvasive and real-time strategy for monitoring cell RVD as well as assessing cell migration, which was expected to supply a new diagnostic tool for metastatic cancers.

Focal adhesion kinase PTK2 autophosphorylation is not required for the activation of sodium-hydrogen exchange by decreased cell volume in the preimplantation mouse embryo.

SummaryRecovery from decreased cell volume is accomplished by a regulated increase of intracellular osmolarity. The acute response is activation of inorganic ion transport into the cell, the main effector of which is the Na+/H+ exchanger NHE1. NHE1 is rapidly activated by a cell volume decrease in early embryos, but how this occurs is incompletely understood. Elucidating cell volume-regulatory mechanisms in early embryos is important, as it has been shown that their dysregulation results in preimplantation developmental arrest. The kinase JAK2 has a role in volume-mediated NHE1 activation in at least some cells, including 2-cell stage mouse embryos. However, while 2-cell embryos show partial inhibition of NHE1 when JAK2 activity is blocked, NHE1 activation in 1-cell embryos is JAK2-independent, implying a requirement for additional signalling mechanisms. As focal adhesion kinase (FAK aka PTK2) becomes phosphorylated and activated in some cell types in response to decreased cell volume, we sought to determine whether it was involved in NHE1 activation in the early mouse embryo. FAK activity requires initial autophosphorylation of a tyrosine residue, Y397. However, FAK Y397 phosphorylation levels were not increased in either 1- or 2-cell embryos after cell volume was decreased. Furthermore, the selective FAK inhibitor PF-562271 did not affect NHE1 activation at concentrations that essentially eliminated Y397 phosphorylation. Thus, autophosphorylation of FAK Y397 does not appear to be required for NHE1 activation induced by a decrease in cell volume in early mouse embryos.

The Volume-Regulated Anion Channel LRRC8/VRAC Is Dispensable for Cell Proliferation and Migration.

Cells possess the capability to adjust their volume for various physiological processes, presumably including cell proliferation and migration. The volume-regulated anion channel (VRAC), formed by LRRC8 heteromers, is critically involved in regulatory volume decrease of vertebrate cells. The VRAC has also been proposed to play a role in cell cycle progression and cellular motility. Indeed, recent reports corroborated this notion, with potentially important implications for the VRAC in cancer progression. In the present study, we examined the role of VRAC during cell proliferation and migration in several cell types, including C2C12 myoblasts, human colon cancer HCT116 cells, and U251 and U87 glioblastoma cells. Surprisingly, neither pharmacological inhibition of VRAC with 4-[(2-Butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inden-5-yl)oxy]butanoic acid (DCPIB), carbenoxolone or 5-nitro-2-(3-phenylpropyl-amino)benzoic acid (NPPB), nor siRNA-mediated knockdown or gene knockout of the essential VRAC subunit LRRC8A affected cell growth and motility in any of the investigated cell lines. Additionally, we found no effect of the VRAC inhibition using siRNA treatment or DCPIB on PI3K/Akt signaling in glioblastoma cells. In summary, our work suggests that VRAC is dispensable for cell proliferation or migration.

Erv14 cargo receptor participates in regulation of plasma-membrane potential, intracellular pH and potassium homeostasis via its interaction with K+-specific transporters Trk1 and Tok1

Cargo receptors in the endoplasmic reticulum (ER) recognize and help membrane and soluble proteins along the secretory pathway to reach their location and functional site. We characterized physiological properties of Saccharomyces cerevisiae strains lacking the ERV14 gene, which encodes a cargo receptor part of COPII-coated vesicles that cycles between the ER and Golgi membranes. The lack of Erv14 resulted in larger cell volume, plasma-membrane hyperpolarization, and intracellular pH decrease. Cells lacking ERV14 exhibited increased sensitivity to toxic cationic drugs and decreased ability to grow on low K+. We found no change in the localization of plasma membrane H+-ATPase Pma1, Na+, K+-ATPase Ena1 and K+ importer Trk2 or vacuolar K+-Cl− co-transporter Vhc1 in the absence of Erv14. However, Erv14 influenced the targeting of two K+-specific plasma-membrane transport systems, Tok1 (K+ channel) and Trk1 (K+ importer), that were retained in the ER in erv14Δ cells. The lack of Erv14 resulted in growth phenotypes related to a diminished amount of Trk1 and Tok1 proteins. We confirmed that Rb+ whole-cell uptake via Trk1 is not efficient in cells lacking Erv14. ScErv14 helped to target Trk1 homologues from other yeast species to the S. cerevisiae plasma membrane. The direct interaction between Erv14 and Tok1 or Trk1 was confirmed by co-immunoprecipitation and by a mating-based Split Ubiquitin System. In summary, our results identify Tok1 and Trk1 to be new cargoes for Erv14 and show this receptor to be an important player participating in the maintenance of several physiological parameters of yeast cells.

Magnetodielectric effect in rare earth doped BaTiO3-CoFe2O4 multiferroic composites

Magnetically switchable dielectric properties in functional multiferroic composites at room temperature is considered to be a great challenge in order to fabricate magnetoelectric devices. High magnetoelectric effect in such materials is possible provided ferroelectric phase is highly coupled to the magnetic phase. In this report, an attempt has been made to fabricate multiferroic composites (1-x) Ba0.95Ho0.05TiO3 – x CoDy0.1Fe1.9O4 (x = 0.03, 0.06 and 0.09) by solid state route, with tunable magnetodielectric properties. From XRD studies, a decrease in cell volume of CoDy0.1Fe1.9O4 phase is observed with the increase in Ba0.95Ho0.05TiO3 phase, which is responsible for higher magnetodielectric effect. In composites, an appreciable decrease in grain size is one of the main factor that drives the coupling between two ferroic phases. By the incorporation of Ho3+ ions in the BaTiO3 lattice, an increase in ε′ is observed, which resulted in improved magnetodielectric effect in composites. In composites, decrease in hopping length with the increase in ferrite phase, resulted in enhancement in dielectric constant. For all composites, the unsaturated ferroelectric hysteresis loops were observed due to the conducting nature of ferrite phase. The incorporation of Dy3+ ions in the CoFe2O4 expanded its lattice, resulting in strain, which highly affected the magnetic properties. The magnetocrystalline anisotropy of composites with multidomain structure was calculated by using Law of approach to saturation, which is directly related to coupling between two ferroic phases. Magnetodielectric studies revealed that the magnetic ordering of CoDy0.1Fe1.9O4 phase results in increase in number of polar domains of Ba0.95Ho0.05TiO3 phase and thereby improves the magnetodielectric effect. The overall results of this work established the unification of Ba0.95Ho0.05TiO3 and CoDy0.1Fe1.9O4 phases in multiferroic composites, with improved coupling, making them potential candidates for magnetoelectric devices.

XPS spectroscopy, structural, magnetic and dielectric investigations of CaGdAlO4 and Yb:CaGdAlO4 single crystals

Materials for ultrafast femtosecond lasers, CaGdAlO4 (CGA) single crystals, undoped and doped nominally with 8% at. of Yb, were grown by the Czochralski method in [100] direction. X-ray analyses showed the ideal disorder on Gd/Ca sites. The decrease of unit cell volume for the crystal doped with Yb was observed. Magnetic measurements revealed that undoped and doped samples were paramagnetic. The real concentration of Yb was determined as 5% at. The XPS lines: O1s, Al2p and Ca2p are complex and they consist of the main line and additional lines at lower and higher binding energy. The intensities of additional lines decrease comparing the end and cone part of crystal, indicating an improvement of crystal structure during the growth process. XPS chemical analyses showed deficiency of Al and Ca and excess of oxygen. The oxygen excess may exist in two contributions: in one, to keep the charge neutrality as Gd-Ox sheets between CGA; the second as interstitial oxygen, responsible for brownish coloration of crystals. Dielectric properties are close to values measured for similar compounds CaYAlO4, CaNdAlO4, and SrLaAlO4.

Effects of iso- and polyvalent substitutions on the short/long-range crystalline order in CuCrO2 compounds

Compounds of pristine CuCrO2, doped CuCr0.96M0.03V0.01O2 (M = Ti, Mn, Ga and Nb), CuCr0.96V0.04O2, CuCr0.97Mg0.03O2, CuCr0.97Ni0.03O2and CuCr1-xFexO2 (x = 0.03, 0.06, and 0.09) were prepared by conventional solid-state route. Rietveld Refinement method using the Fullprof software confirms the single rhombohedral structure with space group R-3m for all the studied samples. It was found that doped ion having a larger ionic radius shows an increase in the unit cell volume for CuCrO2, while the unit cell volume decreases or remains nearly unchanged for dopant having a slightly smaller ionic radius. Negligible strain is observed in the pristine, Mn, Ga and Nb doped samples, whereas other dopants show strained growth. It was found that samples with Ti and Fe doping exhibit the maximum strain. Although, no significant changes in the frequencies of Raman active modes A1g and Eg were detected, strong local distortions were observed in the Mn, Ti and Fe doped samples. In addition, the CuCrO2 compounds doped with V, Ga, Nb, Ti and Mn ions exhibit splitting of IR active Eu and A2u modes.

Sol–gel mediated microwave synthesis of pure, La and Zr doped SnS2 nanoflowers an efficient photocatalyst for the degradation of methylene blue

La and Zr intercalated SnS2 nanostructures have been synthesised using facile sol–gel mediated microwave method. Photocatalytic activity of methylene blue dye was investigated using the synthesized nanosturctures and superior photocatalytic activity was witnessed for the La and Zr intercalated SnS2 than the pure SnS2 nanoflower. It is attributed to the enhanced surface charge carriers and fast electron transport inside the lattice of SnS2. Enlargement on surface active sites in turn increases surface absorption effect due to La and Zr which acts as tentacles to control the recombination process and promotes the higher photoredox reaction. The synthesized nanomaterials were characterized using PXRD, Raman, PL, UV–Vis spectroscopy, FE-SEM and XPS. It is noted from the structural analysis that the decrease in cell volume with increase of doping concentration contributes to Moss-Burstein effect. The increment of band gap and quenching in the photoluminescence effect supported the absorptivity of photoenergies which served as photosensitizer.

Structural and optical characterization of RbLaP4O12:Ln3+ (Ln3+ = Ce3+, Nd3+, Tm3+, or Yb3+).

In this work, for the first time, detailed structural and optical characterization of RbLaP4O12 doped with different concentrations of Ce3+, Nd3+, Tm3+, or Yb3+ ions is reported. The samples were obtained via a precipitation technique. Their structural characterization was performed using X-ray diffraction (XRD), and infrared and Raman spectroscopies. Following XRD data, the unit cell parameters of host lattices were calculated using Rietveld refinement. It was found that an increase in the dopant content leads to a decrease in the unit cell volume. The optical characterization of RbLaP4O12:Ln3+ was carried out by collecting absorption and emission spectra, as well as luminescence decay profiles. Following absorption spectra, the energy band gap of the studied matrix was determined. It was found that the broad absorption band located in the ultra-violet range, in most cases ascribed to charge transfer or f-d transitions, is in fact related to the absorption of the host lattice. The analysis of luminescence properties allowed us to investigate possible ways of depopulation emission levels of impurities.

Effect of dilute doping and non-equilibrium synthesis on the structural, luminescent and magnetic properties of nanocrystalline Zn1-xNixO (x = 0.0025 – 0.03)

We report on the influence of dilute doping combined with the processing conditions on the morphological, structural, chemical states, photoluminescence and magnetic properties of Zn1-xNixO nanopowders. Ni doping changes the ZnO powder morphology from randomly-aggregated nanocrystals to densely-packed nanocrystals arranged in columnar particles, modifies the high-energy-component of O1 s spectrum and increases the modified Auger parameter in XPS, enhances the blue photoluminescence (PL) emission, suppresses the green PL emission and the intensity of the g = 1.997 EPR signal. Ni-ZnO nanostructures show room-temperature ferromagnetism (implying they can serve as dilute magnetic semiconductors). The saturation magnetization, crystallite size and microstrain increase with the doping level; the c-axis constant and unit cell volume decrease, however, being unexpectedly higher with respect to a (reference) ZnO powder with a relaxed lattice. We demonstrate that the investigated properties were controlled by both (dilute) doping level and donor native defects produced by non-equilibrium (oxygen-deficiency and high rate of) ZnO formation.

Influence of Mg2+-substitution on the optical band gap energy of Cr2−Mg O3 nanoparticles

Abstract Chromium oxide (Cr2O3) and Magnesium divalent ions (Mg2+) substituted Cr2O3 nanoparticles were synthesized by wet chemical method. In this report, we have investigated the influence of Mg2+ concentration on the structural and optical properties of Cr2O3 nanoparticles. XRD results demonstrated that pristine Cr2O3 nanoparticles exhibit rhombohedral structure and remains unchanged with Mg2+-substitution. However, it results in strained Cr2O3 nanoparticles with a decrease in lattice parameters and cell volume. The most intense peak centered around 534 cm−1 in Raman spectra depicted a considerable shift when Mg2+ is substituted at Cr3+ sites, complementing our XRD results. In addition, UV–Vis absorption investigation revealed marginal decay of optical band gap from 3 eV to 2.76 eV with the increase of Mg2+ concentration. Refractive index and Urbach energy have also been determined from the UV–Vis analysis and their values found to be increase with Mg2+-substitution.

An Induction System for Clustered Stomata by Sugar Solution Immersion Treatment in Arabidopsis thaliana Seedlings.

Stomatal movement mediates plant gas exchange, which is essential for photosynthesis and transpiration. Stomatal opening and closing are accomplished by a significant increase and decrease in guard cell volume, respectively. Because shuttle transport of ions and water occurs between guard cells and larger neighboring epidermal cells during stomatal movement, the spaced distribution of plant stomata is considered an optimal distribution for stomatal movement. Experimental systems for perturbing the spaced pattern of stomata are useful to examine the spacing pattern's significance. Several key genes associated with the spaced stomatal distribution have been identified, and clustered stomata can be experimentally induced by altering these genes. Alternatively, clustered stomata can be also induced by exogenous treatments without genetic modification. In this article, we describe a simple induction system for clustered stomata in Arabidopsis thaliana seedlings by immersion treatment with a sucrose-containing medium solution. Our method is easy and directly applicable to transgenic or mutant lines. Larger chloroplasts are presented as a cell biological hallmark of sucrose-induced clustered guard cells. In addition, a representative confocal microscopic image of cortical microtubules is shown as an example of intracellular observation of clustered guard cells. The radial orientation of cortical microtubules is maintained in clustered guard cells as in spaced guard cells in control conditions.

Structural, Magnetic, Magnetocaloric and Mössbauer Spectrometry Study of $${\hbox {Gd}}_2{\hbox {Fe}}_{17-x}{\hbox {Cu}}_x$$ Gd 2 Fe 17 - x Cu x ( $$x=$$ x = 0, 0.5, 1 and 1.5) Compounds

The structure, magnetic and magnetocaloric properties of arc-melted $${\hbox {Gd}}_2{\hbox {Fe}}_{17-x}{\hbox {Cu}}_x$$ ( $$x =$$ 0, 0.5, 1 and 1.5) solid solution have been studied. The Rietveld refinement shows that these compounds crystallize in the rhombohedral $${\hbox {Th}}_2{\hbox {Zn}}_{17}$$ -type structure with the $$R{\bar{3}}m$$ space group, and the substitution of iron by copper leads to a decrease in the unit cell volume. The Curie temperature ( $$T_{\mathrm{C}}$$ ) of the prepared samples depends on the copper content. The reduction of the ferromagnetic phase transition temperature from 475 K (for $$x = 0$$ ) to 460 K (for $$x = 1.5$$ ) is due to the substitution of the magnetic element (Fe) by non-magnetic atoms (Cu). The magnetocaloric effect was determined in the vicinity of the Curie temperature $$T_{\mathrm{C}}$$ . By increasing the Cu content, an increase in the values of magnetic entropy ( $$\Delta S_{\mathrm{M}}$$ ) in a low applied field is observed. The preferred inequivalent crystallographic site of Cu atoms was determined by Mossbauer spectrometry analysis based on the isomer shift parameter correlation with the Wigner–Seitz cell volumes.