The structural, elastic, electronic, magnetic, and thermodynamic properties of the all-Heusler Pd2CrGe alloy are investigated using the full-potential linearized augmented plane wave method based on density functional theory. The results show that the Pd2CrGe compound is more stable in the Cu2MnAl type structure compared to the Hg2CuTi type and more stable in the ferromagnetic (FM) state than in the paramagnetic (PM) state. The calculated cohesive energies confirm this result. The structural, electronic, magnetism, and elastics properties, were calculated and analyzed in the Cu2MnAl type in the ferromagnetic ground state. The calculated lattice constant is in good agreement with the available structural data. The band structure and the calculated densities of states (DOS) of this alloy show a metallic behavior. This result was demonstrated by three approaches (GGA, GGA + U, and TB-mBJ). Near the Fermi level, the energy is mainly occupied by Pd-4d and Cr-3d electrons. The calculated total magnetic moment of 3.62 µB is not in agreement with the value of 6 µB of the Slater–Pauling rule. The calculated values of the elastic constants follow the criteria of mechanical stability. The mechanical results show a ductile character. Using the quasi-harmonic Debye model has been employed to study the pressure and temperature-dependent thermodynamic properties of Pd2CrGe.

The role of Sm doping on the structure, vacancy characteristics, valence states of the constituent elements, and magnetic performances of Gd1-xSmxMnO3 (x = 0.00–0.20) ceramics synthesized using the solid-state reaction method is discussed. The X-ray diffraction and Raman spectroscopy results revealed that the orthorhombic perovskite structure with a single phase was formed in all Gd1-xSmxMnO3 ceramics, and the addition of Sm ions induced lattice deformation. The X-ray photoelectron spectroscopy and positron annihilation spectroscopy results showed that the vacancy concentration and Mn4+ content in Gd1-xSmxMnO3 samples initially increased and subsequently decreased as the Sm doping concentration was increased. The magnetic property measurements revealed that Sm doping had a significant impact on the low temperature magnetic ordering of Gd3+ ions, magnetic transition temperatures, and magnetization. From the correlation study between structure and properties, it could be concluded that the development of magnetic characteristics was closely related to the cation vacancies concentration and the creation of Mn4+ in Gd1-xSmxMnO3 samples.

The calcination temperature effects on structural, magnetic, morphological, electrical, and dielectric properties for Mg0.6Co0.2Cu0.2FeCrO4 spinel ferrites have been investigated in this work. The samples (abbreviated as S900 and S1100) were prepared by the sol-gel route and calcined at two different temperatures (900 °C and 1100 °C). The thermogravimetric analysis was used to investigate the weight loss versus temperature and the formation of the spinel phases. The cation distributions were estimated for the samples using experimental XRD patterns based on the Rietveld refinement of the atomic occupancy values. With increasing calcination temperature, unit cell parameters and average crystallite size show an increasing trend. From the magnetic hysteresis loops, low coercive fields were obtained, making Mg0.6Co0.2Cu0.2FeCrO4 ferrites suitable candidates for soft magnetic devices. Nyquist-diagrams modeling shows that the conduction process in the samples is governed by the effect of grain and grain boundary contributions. Impedance and modulus curves show a dielectric relaxation phenomenon in the samples with non-Debye nature. The samples show electrical insulating (I)-semiconducting (S) transitions at TIS = 360 K for S900 and TIS = 400 K for S1100. Both NSPT and CBH models were used to explain the sample conduction process. Due to the increase in crystallite size with increasing calcination temperatures, activation energies decrease from 0.279 to 0.211 eV for S900 and S1100, respectively. In addition, the synthesized materials exhibit low dielectric constants and dielectric losses at higher frequencies as well as high electrical resistivity. These properties make Mg0.6Co0.2Cu0.2FeCrO4 samples suitable candidates for high-frequency applications and microwave absorption devices.

CdS and Cr0.04Cd0.96-xNxS (x = 0, 2, 4, 6, and 8 at %) nanoparticles were synthesized through simple chemical co-precipitation method. The synthesized nanoparticles were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDAX), UV–vis diffuse reflectance spectroscopy (DRS), and vibrating sample magnetometer (VSM). XRD studies confirmed the cubic structure of nanoparticles with a crystallite size of around 1–2 nm. Incorporation of Cr and N elements into the host CdS matrix is confirmed through EDAX analysis. UV–vis DRS spectra of the nanoparticles revealed an enhancement in energy band gap values, and a room temperature ferromagnetism is observed in Cr0.04Cd0.96-xNxS (x = 0, 2, 4, 6, and 8 at %) nanoparticles which is favorable for spintronic applications.

Magnetization measurements have been carried out to study the behavior of isothermal magnetic entropy change and critical magnetic equation of state of EuS. X-ray diffraction data exhibits rock salt-type cubic structure of EuS. Magnetization measurements indicate a ferromagnetic to paramagnetic phase transition at TC ~ 16.8 K. Isothermal magnetic entropy change exhibits nonmonotonic behavior with temperature exhibiting a peak around TC. The peak value systematically increases with the increase of field change ΔH and the peak value, ΔSmax is ~ 45 J/kg K for ΔH of 70 kOe. Arrott plots and superposition of normalized entropy change graphs for different ΔH with respect to rescaled temperature θ indicate the phase transition to be of second-order type. The temperature variation of exponent n of exponential variation of ΔS with ΔH shows nonmonotonic behavior displaying the minimum at TC for n ~ 0.57. The magnetic critical exponents for the system are found to be β = 0.30, γ = 1.32, and δ = 5.32. Furthermore, analysis reveals that long-range exchange interaction is not supported in this system. Deviation of the critical exponents from the isotropic short-range Heisenberg exchange model in this system is surmised due to magnetic anisotropy and dipolar interactions.

In this paper, magnetic and structural properties’ and graphene nanoparticles’ influence on photocatalytic activity of BiFeO3 ceramics are reported. BiFeO3 ceramics were prepared by the sol–gel process and sintering at different temperatures from 400 to 700 °C to get phase pure BiFeO3 ceramics. X-ray diffraction patterns indicated pure phase with sharp peaks for sample sintered at 600 °C. Rietveld analysis showed the presence of pure phase samples of rhombohedral perovskite structure with R3c symmetry expect sample sintered at 700 °C. Bond valance sum analysis showed that Fe cations are inadequately bonded, while the Bi cations are excessively bonded in BiFeO3 structure. First-order Raman modes along with few second-order modes belonging to rhombedral crystal were observed in Raman spectra. X-ray photoelectron spectroscopy showed the presence of mixed oxidation states (Fe2+/Fe3+) with Fe3+ dominance. Vibrating sample magnetometer analysis indicated weak ferromagnetism along with strong dependence of magnetic characteristics on sintering temperatures. The ferromagnetic saturation magnetization (\({M}_{FM}^{S})\) and remnant magnetization decreased from 0.057 to 0.0049 emu/g and 0.0150 to 0.0009 emu/g, respectively, with increasing sintering temperature. The photocatalytic activity of pure BiFeO3 and graphene nanoparticle-modified BiFeO3 samples was recorded. It was observed that BiFeO3 with graphene nanoparticles exhibited good degradation toward methylene blue dye when exposed to visible light irradiation.

The aim of this study is to improve the connectivity and microstructural control of bulk MgB2 via admixed in situ and ex situ syntheses and their effect on flux pinning behavior. Different weight percentages with the ratio of x wt.% ex situ powder were added to 1.0 g in situ powder via a solid state synthesis process where x = 0, 15, 20, 25, and 30, respectively. MgB2 was verified as the predominant phase in all of the samples by X-ray diffraction. With the addition of ex situ powder, magnetization measurements revealed a modest drop in critical temperature, Tc, from 38.5 to 37.8 K. At 20 K, the self-field critical current density, Jc, increased as the co-addition levels increased, owing to enhanced grain coupling. With a 20 wt.% co-addition level, the largest self-field Jc achieved is 348 kA/cm2 showing field dependent Jc of the co-added samples at 20 K is greater than that of the pure sample. The current findings suggest that a small quantity of ex situ powder added to the admix portion of Mg and 2B during synthesis can improve flux pinning and Jc. The reduction in the void volume which enhanced the connectivity of the sintered bulk samples was observed by scanning electron microscopy. Our results show that ex situ-in situ co-synthesis develops the superior connectivity potential of MgB2 bulk superconductor.

Y2FeAlO6 and YReFeAlO6 (Re = Nd, Sm, Gd, Dy) were successfully prepared by the solid-state reaction method. The crystal symmetry and stability are slightly improved under rare-earth substitution. The P-E ferroelectric hysteresis loops show that the YReFeAlO6 (Re = Nd, Sm, Dy, Gd) samples have weak room temperature ferroelectric properties with small remnant polarization (Pr = 0.0037–0.0168μC/cm2), which are slightly weaker than that of Y2FeAlO6 (Pr = 0.0367μC/cm2). The M-H hysteresis loops show that the magnetic properties of YReFeAlO6 (Re = Nd, Sm, Dy, Gd) are dominated by antiferromagnetic interaction, accompanied by weak ferromagnetism. The value of magneto-capacitance for YReFeAlO6 (Re = Nd, Sm, Dy, Gd) is higher than that of Y2FeAlO6, which indicates that the magneto-electric coupling enhances probably due to the decrease in the number of oxygen vacancies and the increase of the Fe3+ content under rare-earth substitution.

The connection between the peak of density of electronic states at ~ 0.4 eV below the Fermi level and the localization of charge carriers at compression of the height of CuO5 pyramids has been found by a comparison of experimental angle-resolved photoemission spectra data for Y0.9Ca0.1Ba2Cu3O6.8 single crystal and calculations of the electronic structure in a framework of the density functional theory. Both experiment and calculation are performed using 34.6 and 90.2 eV photon energy. The excitation energy does not have any noticeable influence on the peak of density of electronic states. Crystal structure distortions on the crystal surface result in observation of localized electronic states below the temperature of superconducting transition.

MnCoSi and MnCoSiB0.5 alloys were obtained by melt-spinning technique in order to attain polycrystalline microstructures with average grain sizes well below 10 microns. Phase distribution studied by X-ray analysis indicated single-phase materials with orthorhombic structure and TiNiSi-type crystal symmetry. Chemical homogeneity was verified by means of scanning electron microscopy, whereas magnetic behavior corresponded to soft magnetic materials with coercivity values lower than 20 Oe and saturation magnetization of 80 emu/g. Magnetocaloric response of these MnCoSiB alloys was characterized by a maximum magnetic entropy change of 1.0 J/kg K (for a magnetic field variation of 2.0 Tesla) and attractive refrigerant capacity over 100 J/kg, which represents a significant enhancement respect to equivalent MnCoGe alloys.

The resistive transition width of a recently discovered room temperature near-ambient-pressure hydride superconductor [1] changes by more than three orders of magnitude between different samples, with the transition temperature nearly unchanged. For the narrowest transitions, the transition width relative to \(T_c\) is only \(0.014 \%\). The voltage-current characteristics indicate vanishing critical current, and the normal state resistance is unusually small. These anomalous behaviors and other issues indicate that this system is not a superconductor. Implications for other hydrides are discussed.

The time-dependent Ginzburg–Landau equations (TDGL) for a type-II superconducting film containing columnar defects are solved by the finite difference method. The effect of the number of defects on the flux dynamics inside the superconducting film is discussed. The effect of the Ginzburg–Landau parameter \(\kappa\) on the vorticity of superconducting films with columnar defects is also analyzed. The results show that the formation of vortices is affected when the superconductor contains columnar defects. In addition, the defects and the Ginzburg–Landau parameter \(\kappa\) also affect the maximum magnitude of the order parameter and the number of defects. Finally, we discuss the relationship between the magnetization of superconducting films with columnar defects and the external magnetic field.

Nanoparticles of formula Co1-xZnxFe2O4 (x = 0.0, 0.3, and 0.5) were prepared successfully using a citrate-auto-combustion method. This work studies the substitution effect of the Zn2+ ion on the physical, chemical, and structural properties of CoFe2O4. The structure of the prepared samples was determined via X-ray diffraction (XRD) and Fourier transformed infrared spectrometer (FTIR). X-ray diffraction of the investigated samples ensures that all the prepared samples crystallite into single structure. There is a variation of crystallite size with change in Zn concentration as it is observed that the crystallite size increased from 16.01 to 30.56 nm by increasing Zn concentration. The Fourier transform infrared spectra (FTIR) in range (390:4000) Cm−1 were used for studying the elastic properties of the prepared spinel ferrites. It is observed that, by increasing Zn concentration, all elastic moduli increased. The morphological and surface study of the calcined samples was investigated by scanning electron microscopy (SEM) and Gwyddion 2.45 software respectively. The roughness average (Ra) was 35.20 nm at x = 0 and increased to 46.6 nm at x = 0.5. At the room temperature, magnetic behavior of the all studied samples was studied. It is observed that the maximum saturation magnetization was 67.611emu/gm and it was related to Co0.7Zn0.3Fe2O4 while the highest value of exchange bias (HEB) was 2.15 Oe for Co0.5Zn0.5Fe2O4. The antibacterial activity of CoFe2O4, Co0.7Zn0.3Fe2O4, and Co0.5Zn0.5Fe2O4 was successfully tested against Escherichia coli and Staphylococcus aureus bacteria. The highest inhibition zone of Co1-xZnxFe2O4 values was 8 and 7.5 mm for E. coli and S. aureus, respectively, and these values were observed for x = 0.5. Generally, these results exhibit a high possible of ferrites for using in antibacterial applications.

The structural, half-metallic, and elastic characteristics of XZrAs (X = Cr, Mn, and V) half-Heusler compounds were theoretically calculated using the WIEN2k code. For the term of the potential exchange and correlation (XC), we calculated structural, electronic, and magnetic properties using the generalized gradient approximation (GGA). The type 1 arrangement in ferromagnetic (FM) phases is more energetically stable than other type arrangements in all compounds. The spin-up electrons of both XZrAs (X = Cr, Mn) half-Heusler compounds in the type III structure are semiconducting with energy gaps, whereas the spin-dn electrons are metallic. Research has also been done on the VZrAs compound, which exhibits metallic characteristics in both type I and type III structures. XZrAs (X = Cr, Mn, and V) half-Heusler compounds are elastically stable and ductile, according to calculated Cij elastic constants. Finally, at equilibrium lattice constants a = 6.1196 A° for MnZrAs and 6.142 A° for CrZrAs, real half-metal ferromagnetic materials (HMF) were produced from XZrAs (X = Cr, Mn) half-Heusler compounds within 3 µB and 2µB, respectively.

In this study, Fe40Ni38Mo4B18 amorphous ferromagnetic ribbon was used as a vibrating reed sensor to detect Fe3O4 magnetic nanoparticles. The sensor surface was not subjected to any treatment: the amorphous ribbon was used directly as a sensor. Nanoparticles with a diameter of 25 nm in ddH2O were dripped on the sensor surface at different rates. Different amounts of magnetic nanoparticles ranging from 1 to 12 µg were dripped, and it was observed that the sensor resonance frequency decreased linearly with the mass of magnetic nanoparticles dripped. It was shown that 1 µg MNP could be easily detected by the vibrating reed method.

The current work involves the use of flash auto combustion procedure to synthesize nano-ferrites Mn0.6Zn0.4LaxFe2-xO4, (x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) annealing at 500 °C for 4 h. X-ray Diffraction (XRD), Fourier transition infrared spectroscopy (FTIR), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structural properties of produced samples. Scanning electron microscopy (SEM) was utilized to examine the surface morphology of the samples at various Lanthanum concentrations. From XRD, the spinel cubic structure for all samples with few traces of secondary phase at high La concentrations is assured. The crystallite size is estimated to be in the nanoscale range of 13.16–18.13 nm using the Debye–Scherrer formula. The appearance of characteristic vibrational bands near 460 cm−1 and 563 cm−1, which correspond to the octahedral and tetrahedral sites, respectively, confirms the formation of the spinel structure. SEM micrographs show that the grains are nearly irregular in shape, and the accumulation of La+3 ions at the grain boundaries exerts tensile strength and pressure on the grain itself, reducing the grain size. The particle size estimated by TEM coincides well with the crystallite size determined by XRD. The thermogravimetric analysis, (TGA), was used to investigate the thermal properties of the nanoferrites from room temperature to 1000 °C. In comparison to the other samples, the sample with x = 0.04 has greater thermal stability and the TEM measurement indicates that this sample has the smallest particle size. Therefore, we can assert that the thermal stability improves as the particle size decreases. The magnetic permeability was measured in the temperature range 303–773 K at a fixed frequency of 10 kHz and at various La contents. The sample with x = 0.04 has a minimal permeability value, showing that the separation brought on by La ions has diminished the super exchange contact between magnetic ions.

We report the preparation, characterization, and magnetic hyperthermia of magnesium-doped maghemite (γ-Fe2O3) nanoparticles (NPs). XRD and Rietveld refinement reveal the formation of a single cubic phase of γ-Fe2O3, where the substitution of Fe+3 located in the tetrahedral site by Mg+2 did not alter the crystal structure. Magnetic measurements showed an increase of saturation for low concentration of magnesium (1% and 3%) and a decrease for 5% of magnesium. The superparamagnetism behavior and the effective anisotropy constant (\({K_{eff}}\)) were confirmed and determined by the Langevin model and the law of approach to saturation (LAS), respectively. Hyperthermia under an alternating magnetic field (AMF) was conducted, indicating that all the NPs reach hyperthermia temperatures (42 °C) in relatively short times (3–5 min.). It was found that all the Mg-doped γ-Fe2O3 NPs present relatively good heating efficiencies, with SAR values in the range of 35–114W/g and ILP values (0.58–1.67 nHm2/kg). Furthermore, the linear response theory (LRT) model was studied to further assess heating mechanisms and to determine the Néel relaxation time (\({\tau }_{R}\)). Our finding strongly suggests that the as-prepared Mgx-doped γ-Fe2O3 MNPs are promising for hyperthermia application.

The superconducting properties of alkaline doped Iron based superconductors (L=Li, Na, K, Rb, Cs) compounds were investigated using the ab-initio method. The studies were concentrated on investigatingthe electronic band structure, Fermi surface and superconducting properties of these materials. These compounds are having tetragonal structure (space group=129) with the P4/nmm. Plane wave calculations were performed by Wien2K code using the self-consistent method. To study the electronic structure and magnetic ordering, the Brich-Murnaghan equation was used. The estimated lattice parameters are comparable with the available experimental data. Density of states values at the Fermi level are found to increase continuously with increasing ionic radius of the dopent ion. The low value of electron phonon coupling constant may be attributedto increase in bond angle of A-Fe-A, Fe-A distances and degraded Fermi surface nesting. The absolute Fe magnetization of LiFeAs and NaFeAs are larger than other Alkali (A= K, Rb, Cs) compounds. Finally, the electron-phonon coupling constant (λ) values are found to decrease continuously

The ordered multiphase composition is a way to obtain materials with necessary magnetic and electrical transport properties. The ternary phases of La2Cu3Al8 and Ce2Cu3Al8 are prepared by arc-melting high purity starting elements on a copper hearth under argon atmosphere. The elemental analysis (EDX) shows sample composition as 2:3:8 mean ratio for both La and Ce compositions; however, X-ray powder diffraction reveals a composite of two ternary phases and some unreacted aluminum. Magnetic and electrical properties were investigated as a function of temperature and magnetic field on a commercial instrument. The thermodynamics of sample formation is very critical for the phase formation of R-Cu-Al compounds as almost identical mixed phases have been observed from Rietveld analysis for both La and Ce compounds. In addition to these observations regarding structure, it is interesting to observe weak antiferromagnetism and magnetic relaxation in the cerium compound exhibiting highly frustrated magnetic ground state. Both the samples have been found to be metallic till the lowest temperature of measurement.

The phases, microstructure, and magnetic properties in a severely deformed Cr-Ni–Al alloy have been studied. The eutectic microstructure observed in localized regions of the alloy can be interpreted as a result from the super-Arrhenius relaxation of the alloy. According to X-ray diffraction and magnetometry, the nanosized nickel inclusions in the matrix of the chromium-nickel γ-solid solution are formed. It is shown that, after severe (superplastic) deformation, a unidirectional magnetic anisotropy is induced, which may be associated with the antiferromagnetic coupling between the CrNi2 matrix and the nickel inclusions.