Increase In Lattice Parameter Research Articles

Effect of cobalt doping on the structural, magnetic, optical, and electronic properties of LiFeCr4O8

Cobalt doping's influence on the structural, magnetic, and electronic properties of the double spinel LiFeCr4O8 was systematically investigated. Rietveld refinement revealed a consistent increase in lattice parameter a and unit cell volume with cobalt incorporation. Magnetic susceptibility measurements indicated three distinct transitions: an increase in the ferrimagnetic transition temperature (TN), a decrease in the magnetostructural transition temperature (TMS), and an increase in the spin gap transition by cobalt doping. Through diffuse reflectance spectroscopy the direct optical band gap (Eog) was obtained with values of 1.169 eV, 1.303 eV, 1.396 eV, and 1.230 eV for x = 0.0, 0.1, 0.2, and 0.5, respectively. The observed increase in Eog with cobalt doping suggests a widening of the band gap, which could be beneficial for optoelectronic applications. By means of X-ray photoelectron spectroscopy (XPS) the core levels of Li 1s, Co 3p, Fe 3p, Cr 3p, Fe 2p, Cr 2p, and O 1s were identified. XPS valence band (VB) analysis revealed a decreasing intensity at binding energy BE = 0 eV with respect to x = 0.0. Density functional theory calculations with Hubbard U correction (DFT + U) confirmed a ferrimagnetic semiconductor behavior with a direct electronic band gap (Eeg) of 1.085 eV.

Structure and mechanical properties of TiAlTaN thin films deposited by dcMS, HiPIMS, and hybrid dcMS/HiPIMS

The quaternary Ti1-x-yAlxTayN system exhibits superior thin film properties compared to Ti1-xAlxN. Apart from the Ta content, the sputtering method has a crucial effect on the structural and mechanical properties. High power impulse magnetron sputtering (HiPIMS) produces denser thin films with improved hardness compared to direct current magnetron sputtering (dcMS), but at lower deposition rates. However, a hybrid dcMS/HiPIMS process combines the advantages of dcMS and HiPIMS and is, therefore, a suitable method to synthetize Ti1-x-yAlxTayN thin films. To analyze the effect of the sputtering technique on the structural and mechanical properties, Ti1-x-yAlxTayN is sputtered from TiAlTa compound targets with Ta fractions up to 0.2 by dcMS, HiPIMS, and dcMS/HiPIMS.The Ta metal fraction within Ti1-x-yAlxTayN steadily increased up to y ≈ 0.25, while the Al content notably decreased at higher Ta levels. This reduction was most pronounced in HiPIMS, resulting in an order of decreasing Al content as dcMS, dcMS/HiPIMS, and HiPIMS. All thin films exhibit a Ti1-x-yAlxTayN substitutional solid solution with a linearly increasing lattice parameter corresponding to higher Ta contents. At similar Ta contents, HiPIMS-Ti1-x-yAlxTayN and dcMS/HiPIMS-Ti1-x-yAlxTayN show larger out-of-plane lattice parameters compared to dcMS/HiPIMS-Ti1-x-yAlxTayN, indicating elevated compressive stresses within the thin films. The Ti1-x-yAlxTayN thin films show a column-like structure, with HiPIMS promoting the formation of a denser morphology with less columns. The HiPIMS-Ti1-x-yAlxTayN with H = 41 GPa and dcMS/HiPIMS-Ti1-x-yAlxTayN with H = 40 GPa achieve their peak hardness at a lower Ta metal fraction of y ≈ 0.12–0.13, in contrast to dcMS-Ti1-x-yAlxTayN, which reaches H = 38 GPa at y ≈ 0.25. The shift to lower Ta contents for the maximum hardness in HiPIMS-Ti1-x-yAlxTayN and dcMS/HiPIMS-Ti1-x-yAlxTayN is due to higher compressive stresses and smaller crystallite sizes in these films at low Ta metal fractions. The H/E and H3/E2 ratios of the HiPIMS-Ti1-x-yAlxTayN and dcMS/HiPIMS-Ti1-x-yAlxTayN exhibited a similar trend of increasing values, reaching a maximum, and then decreasing with higher Ta content. Consequently, the hybrid dcMS/HiPIMS process produces Ti1-x-yAlxTayN thin films with mechanical properties comparable to pure HiPIMS, making it a suitable sputtering method for the synthesis of Ti1-x-yAlxTayN.

Influence of cationic vacancy diffusion on the aging behavior of low-temperature SrCo1-xRuxO3 thermosensitive ceramics

The thermosensitive ceramics of negative temperature coefficient (NTC), SrCo1-xRuxO3 (0 ≤ x ≤ 0.8), were synthesized using the solid-phase method. The research systematically explored the phase structure, microstructure, elemental chemical states, electrical properties, and aging performance. X-ray diffraction (XRD) data indicates that with the increase of Ru content, the lattice parameter increases. Scanning electron microscopy (SEM) images reveal a dense and uniform microstructure. X-ray photoelectron spectroscopy (XPS) data indicates the presence of Co2+/Co3+ and Ru4+/Ru5+ ion pairs. Resistive temperature data indicates its potential use as a low-temperature thermosensitive resistance material in the range of 2–300 K. Fitting the resistance-temperature curve using the thermally activated band conduction model and Mott's 3D variable range hopping model. Proposed the Ru–O2--Co hopping model, elucidating the hole hopping transport mechanism in NTC ceramics. Impedance spectroscopy analysis indicates that grain boundary resistance dominates the overall resistance of the sample. After aging at 77 K for 864 h, the maximum aging drift rate of the ceramic material is 1.55 %. Proposed a novel cationic vacancy diffusion model to explain aging phenomena, offering a new perspective for designing high-stability low-temperature NTC thermistors.

Mean-field model for BaFe[formula omitted]Ti[formula omitted]O19 ([formula omitted] 0 and 0.2) hexaferrite: Structural and magnetic properties

An experimental and theoretical investigation of the magnetic properties of Ti-doped barium hexaferrite (BaM) is conducted. Polycrystalline samples of BaFe12−xTixO19 with x≤ 0.2 were synthesized using the solid-state reaction method. X-ray diffraction (XRD) analyses, along with Rietveld refinement, confirmed the presence of BaFe12O19 as the predominant BaM phase and a minor amount of hematite in all samples. Structural analysis revealed a slight increase in lattice parameters a and c for x=0.2. A result mostly related to the preferential occupation of Ti4+ ions at the 4f2 and 12k sites, coupled with the reduction of Fe3＋ ions to Fe2＋. It was also found that the magnetic response of samples is affected by Ti4+ substitution. Saturation magnetization slightly decreased from ∼ 45 (x= 0) to ∼ 44 emu/g (x= 0.2), the anisotropy constant from ∼4.08× 105 to ∼4.06× 105 erg/g2, while coercivity slightly increased from ∼ 2456 to ∼ 2468 Oe, and the anisotropy field from ∼ 18.2 to ∼ 18.6 kOe. The magnetic features of the samples were analyzed in terms of a proposed model based on the mean-field theory. Results indicated that the substitution of Ti4+ ions resulted in a decrease in the magnetic moment of the 2b sublattice. Such behavior is influenced by its closest neighboring sites 12k and 4f2 sublattices, which are the preferred occupancy sites for the Ti4+ cations.

Effect of F− doping on structural, elastic, and electronic properties of SmO1−xFxBiS2: A first principles investigation

Structural, elastic, and electronic properties of SmO1−xFxBiS2 were studied using first principles method, and effects of F− doping were clearly observed. By increasing x, the increase of lattice parameter ‘a’ and decrease of ‘c’ are mainly due to the displacement of S1 and Sm atoms respectively. For x = 0.3, new (Bi–S1)2 bonds formation was observed. The gap between Bi- and S1-planes decreases and disappeared at x = 0.9. Cauchy pressures, B/G, and ν indicate ductile nature having metallic bonds with small ionic contribution. B, G, and E are highly anisotropic and show anomaly at x = 0.3, 0.5, and 0.8. Sm 4f states are mainly responsible for metallicity. For x = 0.3, total DOS decreases due to new bonds formation. Anomalous displacement of Sm-sites by doping at O- or Sm-sites induces anomalous displacement of S1 atoms which may be the main reason for change of different properties of SmO1-xFxBiS2.

Prior implantation of hydrogen as a mechanism to delay helium bubbles, blistering, and exfoliation in titanium

This study explores the delaying of the formation of helium bubbles and blisters in pure titanium by hydrogen pre-implantation. Titanium, implanted with helium (40 KeV, 5 × 1017 ions/cm²), exhibited large bubbles that cause exfoliation after heat treatment, whereas hydrogen pre-implantation inhibited bubble growth at room temperature and reduced the exfoliation after heat treatment.In the samples pre-implanted with hydrogen, we found evidence of helium diffusion delay by: (a) a fourfold reduction in bubble pressure (b) faceted cavities in the samples (c) a smaller increase in titanium lattice parameters (d) a 16-fold reduction in average bubble size and a sixfold reduction in bubble area fraction (e) a more than twofold decrease in exfoliation (f) a tendency toward the formation of larger bubbles as a result of heat treatment. We believe that it is reasonable to assume that the inhibition of helium diffusion between tetrahedral interstitial lattice sites takes place because of the occupation of the intermediate octahedral sites by hydrogen atoms.Evidence for the opposite effect, that is inhibition of the diffusion of hydrogen in the presence of helium, is found in the retention of hydrogen in the specimens at elevated temperatures. This retention allowed the existence of titanium hydride after heat treatment at 680 °C. The present study sheds light on the intricate interplay between hydrogen and helium in titanium, providing insights into mechanisms that can potentially mitigate helium-induced damage in materials.

Effect of particle size and composition on local magnetic hyperthermia of chitosan-Mg1-xCoxFe2O4 nanohybrid.

In this study, Mg1-xCoxFe2O4 (0≤x ≤ 1 with ∆x = 0.1) or MCFO nanoparticles were synthesized using a chemical co-precipitation method and annealed at 200, 400, 600, and 800°C respectively to investigate the structural properties of the materials by X-ray diffractometer (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). Controlled annealing increased particle size for each value of x. The aim was to investigate how specific loss power (SLP) and maximum temperature (Tmax) during local magnetic hyperthermia were affected by structural alterations associated with particle size and composition. The lattice parameter, X-ray density, ionic radius, hopping length, bond length, cation-cation distance, and cation-anion distance increase with an increase in Co2+ content. Raman and FTIR spectroscopy reveal changes in cation distribution with Co2+ content and particle size. Magnetic properties measured by the physical property measurement system (PPMS) showed saturation magnetization (Ms), coercivity (Hc), remanent magnetization (Mr/Ms), and anisotropy constant (K1) of the Mg1-xCoxFe2O4 nanoparticles increase with Co2+ content and particle size. When exposed to an rf magnetic field, the nanohybrids experienced an increase in both the SLP (specific loss power) and Tmax (maximum temperature) as the particle size initially increased. However, these values reached their peak at critical particle size and subsequently decreased. This occurs since a modest increase in anisotropy, resulting from the presence of Co2+ and larger particle size, facilitates Néel and Brownian relaxation. However, for high anisotropy values and particle size, the Néel and Brownian relaxations are hindered, leading to the emergence of a critical size. The critical size increases as the Co2+ content decreases, but it decreases as the Co2+ content increases, a consequence of higher anisotropy with the increase in Co2+. Additionally, it is noteworthy that the maximum temperature (Tmax) rises as the concentration of nanohybrids grows, but the specific loss power (SLP) decreases. An increased concentration of chitosan-MCFO nanohybrids inhibits both the Néel and Brownian relaxation processes, reducing specific loss power.

Cationic migration effect on the dielectric and magnetic properties of CoFe2O4/ZnO composites

The present paper focusses on the effect of cationic migration in the sintered CoFe2O4/ZnO composite. The increase in lattice parameter of the CoFe2O4 after sintering indicates substitution of Zn. Mӧssbauer analysis of the samples indicates the transformation of composites to paramagnet in the sample sintered at 600 and 750 °C. At 900 °C, a low hyperfine field sextet was evolved complimented by MH loop which is due to redistribution of cations and formation of ferromagnetic phase. Maxwell-Wagner dispersion was identified by the frequency-dependent fluctuation of dielectric constants (ε׳) and dielectric loss (tan δ). Dielectric constant values of 8.66, 7.90, 9.31 and dielectric loss value of 0.11, 0.03, 0.05 were found for CZ6, CZ7 and CZ9 respectively at 1 MHz frequencies. The composite are suitable for high frequency applications due to its low loss, high resistance, low sintering temperature. The mechanisms behind these observations are discussed in this paper.

Effects of structural strain and phase transformations on the mechanical properties of alumina-zirconia-graphene composites

Yttria-stabilized-zirconia (YSZ) plus graphene-based-materials composites may present phase transitions. Consequently, it may affect the composite properties. Thus, this work discusses the causality between lattice strain, phase transition, fracture toughness (Kc) and hardness (H) values in alumina+YSZ matrix reinforced with 0 wt.% up to 1.25 wt.% multilayered-graphene (MLG). The conventional sintering was made in a reducing atmosphere. H and Kc were obtained by Vickers indentation. The structural characterization shows that the MLG addition promoted an increase in YSZ lattice parameters and a phase transition, from tetragonal to cubic. As a result, the optimum reinforcement peak in the H and in the Kc happens in different MLG concentrations. The Kc optimum is in lower MLG amount, explained by microstructural features. On the other hand, the optimum H displaced to higher MLG concentration may be effect of increasing lattice parameters and the cubic-YSZ phase proportion.

Improved electrochemical properties of Lu-doped LiNi0.5Mn1.5O4 cathode materials for 5 V lithium-ion batteries

LiNi0.5Mn1.5O4 (LNMO) is considered as a promising cathode material for the next-generation high-energy–density lithium-ion batteries. However, the application of LNMO is hindered by its severe Mn dissolution and capacity decay at high voltages. To address this issue, a novel LiNi0.5-x/2Mn1.5-x/2LuxO4 (x = 0, 0.005, 0.02, 0.04) material was successfully prepared using a solid-state method to investigate the effects of phase structures and morphologies induced by Lu3+ doping on the electrochemical properties of the LNMO. When compared to the pristine LNMO material, the LNMO doped with Lu3+ exhibited a significant increase in lattice parameters, resulting in a larger lithium-ion diffusion channel. Furthermore, the truncated octahedral structure enhanced the contact area with the electrolyte, leading to a substantial decrease in Mn3+ concentration. It's noteworthy that the LiNi0.49Mn1.49Lu0.02O4 (LNMO-Lu0.02) sample exhibits the most favorable electrochemical properties. After 200 charge–discharge cycles at a current density of 1 C, the LNMO-Lu0.02 sample demonstrates a discharge capacity of 129.54 mAh/g with a capacity retention rate of 97.46 %. Even at a high current density of 20 C, it maintains a discharge capacity of 107.19 mAh/g, which is much better than the pristine sample. The results indicate a significant improvement in the electrochemical properties and structural stability of Lu-doped LNMO cathode materials.

Structural aspects of dehydration of NaBiO3-based compounds probed by XRD and NMR

The phase transformation in a mixture of hydrated NaBiO3 · nH2O and dehydrated NaBiO3 phase is studied during heating. The results indicate that generally the transformation occurs in two stages. At the first stage the hydrated NaBiO3 · nH2O phase converts to an anhydrous defective intermediate phase with the ilmenite-type structure similar to the initial dehydrated NaBiO3, but with increased lattice parameter c. According to nuclear magnetic resonance (NMR) the intermediate phase is associated with additional inequivalent Na. In terms of the Na–O interatomic distances the intermediate phase is closer to the hydrated phase, but in terms of the symmetry of Na coordination polyhedron it is already closer to the dehydrated one. The Na of the intermediate phase still remains in the sample after the complete dehydration and at the second stage there is a gradual recrystallization of the intermediate phase towards the initial NaBiO3 phase.

Thermoelectric properties of Gd and Se double substituted tetrahedrite.

The compound Cu12Sb4S13, known as tetrahedrite, is an eco-friendly p-type thermoelectric material with earth-abundant, low-cost, and less toxic constituents. This contemporary work studied the thermoelectric properties of Gd and Se double-substituted tetrahedrites. The samples with nominal composition Cu11.95Gd0.05Sb4S13-xSex (where x = 0, 0.2, 0.4, 0.6, and 0.8) were prepared using the solid-state synthesis and sintered using high vacuum hot pressing. The structural analysis using X-ray diffraction revealed a successful tetrahedrite phase formation, and the systematic increase of lattice parameters with the selenium content (x) indicated successful Se substitution. The electron probe microanalysis revealed the presence of secondary phases Cu3SbS4, CuSbS2, and CuGdS2. The Raman spectroscopy showed a weakening Sb-S/Se bond with increased Se content in the samples. The +3 and -2 oxidation states of Gd and Se, respectively, were confirmed from the XPS study. Gd3+, a higher valence substituent at the Cu+/Cu2+ tetrahedral site, helped reduce the carrier concentration. On the other hand, the isoelectronic substitution of Se2- for S2- enhanced the thermopower and power factor by introducing resonant energy states near the Fermi level. Consequently, a maximum power factor of ∼1.35 (±0.08) mW m-1 K-2 at ∼729 K was obtained for the sample x = 0.4. The sample x = 0.4 also exhibited the lowest thermal conductivity ∼ 1.18 (±0.04) W m-1 K-1 at 729 K. The Callaway model indicates that the lowering in the lattice thermal part of conductivity of this sample is due to the combined effect of point defect and Umklapp scattering. The simultaneous improvement of carrier concentration and thermal conductivity resulted in a relatively high zT of ∼0.83 (±0.09) in the x = 0.4 sample.

Enhancing the electrochemical performance of single-crystal LiNi0.8Co0.1Mn0.1O2 cathode material by phosphorus doping

High nickel ternary cathode materials display high specific capacity and low cost, but still suffer irreversible phase change, side reaction and particle cracking during the electrochemical reaction processes. Herein, a P-doped single crystal Ni-rich cathode material is designed, which shows excellent lithium-ion insertion/extraction capability. The phase transition (H1 → H2 → H3) is relieved by the accumulation of interfacial force due to P-doping, as which increases the charge density and promotes the electrostatic repulsion between oxygen layers. P-doping also leads to an increase of lattice parameter c, and the increased thickness of lithium layers and transition metal layers expands the two-dimensional diffusion channel of lithium-ion in the layered structure, facilitating the lithium-ion insertion/extraction processes. The doped ternary single crystal cathode material demonstrates a stable surface structure with resistance to environmental erosion. This work demonstrates that the P-doping is promising to further improve ternary single crystal cathode material for superior lithium-ion battery applications.

Influence of substitutional defects on the structural and magnetic properties of barium hexaferrites

A computational analysis is conducted to understand the impact of Al and Sr substitutions on the structural and magnetic properties of M-type barium hexaferrite (BaFe12O19 or BFO). Al substitutions in BFO led to concentration-dependent increases in lattice parameters and magnetocrystalline anisotropy energy (), while the magnetic moment showed a decline. In contrast, Sr substitutions influenced the lattice differently, reducing parameters but enhancing both and the spin magnetic moment, especially under varying Coulomb interaction () conditions. It’s noteworthy that the value reached approximately 1.03 meV with full Sr substitution. Furthermore, SrFe12O19 (SFO) consistently outperformed BFO in terms of exchange interaction parameters. These findings offer valuable insights for the development and optimization of next-generation magnetic materials.

Influence of Ce3+ ion doping on structural, morphological, magnetic, dielectric and optical properties of Mg0.5Ni0.5Fe2-xCexO4 (0 ≤ x ≤ 0.1) ferrite nanoparticles synthesized via coprecipitation method

In this work the effect of Ce3+ ion doping on microstructure, crystallite size, magnetic, optical and dielectric characteristics of Mg0.5Ni0.5Fe2-xCexO4 (0 ≤ x ≤ 0.1) ferrite nanoparticles are discussed which are synthesized by using the co-precipitation method. The X-ray diffraction analysis confirms the cubic phase of all the synthesized samples and further confirmation of ferrite structure is supported by Fourier transformed infrared spectroscopy characteristic peaks. The crystallite size was determined in the range of 6 nm to 12 nm with increasing lattice parameter value from 8.347 Å to 8.359 Å on increasing Ce3+ ion doping. High-resolution transmission electron microscopy analysis confirms the spherical shape of the nanoparticles with agglomeration. Magnetic hysteresis curves analysis reveals that saturation magnetization of the Mg-Ni ferrite nanoparticles decreases with increasing Ce3+ ion concentration. Vibrating sample magnetometer analysis confirms the superparamagnetic nature of the synthesized samples. Electron spin resonance spectroscopy confirmed the reduction in g-value and spin relaxation time with increasing Ce3+ ions doping. The band gap increases from 1.79 eV to 2.59 eV with increasing Ce3+ ion doping. The magnetic properties of the synthesized samples make these nanoparticles a potential candidate for the synthesis of ferrofluids and biomedical application. Dielectric study confirms the decrease in dielectric constant (ε′) and loss tangent (tan δ) against increasing frequency with increasing Ce3+ ion concentration making the nanoparticles a potential candidate for the high frequency applications.

Synthesis and microstructure of (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2-δ high-entropy oxides characterized by fluorite structure

In this work, single-phase (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2-δ high-entropy fluorite oxides (HEFOs) were successfully prepared by conventional solid-phase reaction method and crystal structure and microstructure were studied in-depth. Single-phase (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2-δ is formed at 1600 °C for 12 h, and five cationic elements are uniformly distributed without any segregation at the micrometer and nanometer scales. And the XRD patterns with Rietveld refinement reveal the formation of single-phase fluorite structure of (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2-δ. The SAED patterns on the [0 1‾ 1] band axes are similar to the diffraction patterns of face-centered cubic fluorite structure, and the standard deviation of the cation radius (coordination VIII) distribution of the specimens is 0.1277, which is again identified as forming a single-phase fluorite structure. The bulk specimens are solid compacts free of obvious cracks with randomly distribution porosity at a rare level, and the powder specimens are irregular fragmented shapes with an average particles size of 5.41 μm. The average cation radius and interplanar spacings becomes larger compared with standard fluorite structure of CeO2 due to the cation radius of La3+, Sm3+ and Nd3+ are larger than that of Ce4+, leading to an increase in lattice parameters of the HEFOs. In addition, the concentration of Ce3+ in the Ce cation is only 8.1 %, and the δ-value is calculated to be 0.3081 based on the content of all cations per mole of the substance, which indicates that the composition of the prepared specimen is (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O1.6919.

Lattice Deformation of Tb0.29Dy0.71Fe1.95 Alloy during Magnetization.

In Tb-Dy-Fe alloy systems, Tb0.29Dy0.71Fe1.95 alloy shows giant magnetostrictive properties under low magnetic fields, thus having great potential for transducer and sensor applications. In this work, the lattice parameters of Tb0.29Dy0.71Fe1.95 compounds as a function of a magnetic field were investigated using in situ X-ray diffraction under an applied magnetic field. The results showed that the c-axis elongation of the rhombohedral unit cell was the dominant contributor to magnetostriction at a low magnetic field (0-500 Oe). As the magnetic field intensity increased from 500 Oe to 1500 Oe, although the magnetostrictive coefficient continued to increase, the lattice constant did not change, which indicated that the elongated c-axis of the rhombohedral unit cell rotated in the direction of the magnetic field. This rotation mainly contributed to the magnetostriction phenomenon at magnetic fields of above 500 Oe. The structural origin of the magnetostriction performance of these materials was attributed to the increase in rhombohedral lattice parameters and the rotation of the extension axis of the rhombohedral lattice.

Entropy change reversibility in MnNi1−x Co x Ge0.97Al0.03 near the triple point

The nature of the phase transition has been studied in MnNi1−x Co x Ge0.97Al0.03 (x= 0.20–0.50) through magnetization, differential scanning calorimetry and x-ray diffraction measurements; and the associated reversibility in the magnetocaloric effect has been examined. A small amount of Al substitution for Ge can lower the structural phase transition temperature, resulting in a coupled first-order magnetostructural transition (MST) from a ferromagnetic orthorhombic to a paramagnetic hexagonal phase in MnNi1−x Co x Ge0.97Al0.03. Interestingly, a composition-dependent triple point (TP) has been detected in the studied system, where the first-order MST is split into an additional phase boundary at higher temperature with a second-order transition character. The critical-field-value of the field-induced MST decreases with increasing Co concentration and disappears at the TP (x= 0.37) resembling most field-sensitive MST among the studied compositions. An increase of the hexagonal lattice parameter a hex near the TP indicates a lattice softening associated with an enhancement of the vibrational amplitude in the Ni/Co site. The lattice softening leads to a larger field-induced structural entropy change (structural entropy change≫ magnetic entropy change, for this class of materials) with the application of a lower field, which results in a larger reversibility of the low-field entropy change (|ΔS rev| = 6.9 J kg−1 K for Δμ 0 H = 2 T) at the TP.

Impact of nickel substitution on structural, dielectric, magnetic, and electrochemical properties of copper ferrite nanostructures for energy storage devices

Nickel-substituted copper ferrite nanoparticles (NP) (Cu1-xNixFe2O4) were prepared using a cost-effective hydrothermal method. X-ray diffraction (XRD) pattern revealed a single-phase cubic spinel structure. The increase in lattice parameters and decrease in crystallite size are associated with the replacement of Cu ions by Ni ions in the host lattice of copper ferrite. The optimized Cu0.95Ni0.05Fe2O4 composition was subsequently annealed at 750 °C and 850 °C for further studies. Fourier transform infrared (FT-IR) analysis shows the existence of two promising fundamental adsorption peaks at 465 and 582 cm−1, related to the metal ion stretching vibrations at the tetrahedral (A) and octahedral (B) sites, respectively. The local disorder at both the A and B sublattices upon the incorporation of Ni was observed from the Raman analysis. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) images shows the formation of agglomerates composed of nano-sized spherical particles. A high Barrett-Joyner-Halenda (BJH) surface area was achieved 17.25 m2/g with a particle stability of −11.1 mV obtained by the zeta potential. Both the dielectric loss and dielectric constant are decreased, whereas the AC conductivity gets increased with increasing frequency. The magnetization-field hysteresis curves exhibited ferromagnetic behavior with a pseudo-single domain, and the cyclic voltammetry study revealed a pseudocapacitive trend. This study highlights the importance of Ni substitution to control the physicochemical properties of spinel-phase CuFe2O4 for diverse applications, such as energy storage and lithium-ion batteries.

Comparative Study of Magnetic Properties of (Mn1−xAxIV)Bi2Te4 AIV = Ge, Pb, Sn

We investigated the magnetic properties of the antiferromagnetic (AFM) topological insulator MnBi2Te4 with a partial substitution of Mn atoms by non-magnetic elements (AIV = Ge, Pb, Sn). Samples with various element concentrations (10–80%) were studied using SQUID magnetometry. The results demonstrate that, for all substitutes the type of magnetic ordering remains AFM, while the Néel temperature (TN) and spin-flop transition field (HSF) decrease with an increasing AIV = Ge, Pb, Sn concentration. The rate of decrease varies among the elements, being highest for Pb, followed by Sn and Ge. This behavior is attributed to the combined effects of the magnetic dilution and lattice parameter increase on magnetic properties, most prominent in (Mn1−xPbx)Bi2Te4. Besides this, the linear approximation of the experimental data of TN and HSF suggests higher magnetic parameters for pure MnBi2Te4 than observed experimentally, indicating the possibility of their non-monotonic variation at low concentrations and the potential for enhancing magnetic properties through doping MnBi2Te4 with small amounts of nonmagnetic impurities. Notably, the (Mn1−xPbx)Bi2Te4 sample with 10% Pb substitution indeed exhibits increased magnetic parameters, which is also validated by local-probe analyses using ARPES. Our findings shed light on tailoring the magnetic behavior of MnBi2Te4-based materials, offering insights into the potential applications in device technologies.