Copper substitution effects on YBCO microstructure: oxygen ordering, structural coherence and superconductivity

A systematic first-principles study is carried out to elucidate how partial Fe substitution at the Mn site (x = 0.25) tunes the structural, electronic, magnetic, elastic, phonon, and thermoelectric properties of MnNiZ (Z = Sb, Bi) half-Heusler compounds using the FP-LAPW method within GGA, GGA+U, and TB-mBJ+U frameworks. Total-energy calculations show that the ferromagnetic phase is the ground state for all pristine and Fe-doped systems, with Fe incorporation preserving the cubic lattice while reducing the symmetry from F-43m to P-43m and maintaining negative formation energies (Δ Hf ≈ −2.31 to −1.67 Ry), thus confirming thermodynamic stability. Phonon dispersions of MnNiSb and MnNiBi exhibit no imaginary modes over the Brillouin zone, demonstrating dynamical stability of the parent phases. MnNiSb and Mn 0.75 Fe 0.25 NiSb display robust half-metallicity with spin-down band gaps of about 0.46–0.66 eV, whereas MnNiBi:Fe undergoes a correlation-driven transition from metallic to half-metallic behavior, developing a minority-spin gap of 0.43–0.48 eV within GGA+U and TB-mBJ+U. Fe doping markedly enhances ferromagnetism, increasing the total magnetic moment from ∼4 μB in the pristine compounds to 7 μB per formula unit in both Mn 0.75 Fe 0.25 NiSb and Mn 0.75 Fe 0.25 NiBi. Elastic constants satisfy the Born stability criteria and reveal ductile behavior, while Fe addition strengthens shear rigidity (C 44 up to ∼70 GPa) and slightly reduces elastic anisotropy compared with the undoped phases. Boltzmann-transport calculations indicate that Fe substitution significantly suppresses lattice thermal conductivity and induces pronounced temperature-dependent thermoelectric responses, with enhanced Seebeck coefficients and improved ZT values relative to the parent compounds over a broad temperature range. These findings demonstrate that Fe substitution is an effective route to simultaneously reinforce ferromagnetism and optimize transport properties in Mn-based half-Heusler alloys for spintronic and thermoelectric applications.

Anisotropic Chemical Pressure Effect on the Antiferromagnetic Kondo Semiconductor Ce(Ru1-xFex)2Al10

We have studied synthetic Fe-substituted hydroxyapatite Ca5-xFex(PO4)3OH and the corresponding deuterated samples with varying Fe concentrations x (0 ≤ x ≤ 0.3) by Raman and IR spectroscopy at room temperature. In the IR spectra, substitution of deuterons for protons affects the OH internal mode in a way consistent with the mass difference of the substituting ions, as well as a mode attributed to vibrations of the Ca3-(OH) unit. In the Raman spectra, the frequency of all modes is not noticeably affected by the Fe substitution. Raman bands show increased width and substantial reduction in intensity with increasing amount of Fe, presumably related to disorder introduced by the substitution. We find that the disorder is smaller in the hydroxyapatites compared to the deuterated ones.

We report on the effect of Fe substitution in the self doped manganite, La0.87Mn1−xFexO3 in the composition range 0 ⩽ x ⩽ 0.15. The electrical resistivity (ρ) and dc magnetization were measured as a function of temperature, field and time. The metal to semiconducting transition is clearly observed for x ⩽ 0.02, while a semiconducting temperature dependence of resistivity is noticed for x ⩾ 0.08. The compound with x = 0.05 shows interesting features of ρ in field-cooled (FC) condition such as bifurcation in the zero-field cooled and FC temperature dependence, weak thermal hysteresis and memory effect. We observe the enhancement of colossal magnetoresistance by the Fe substitution in the low substitution range. The paramagnetic to ferromagnetic transition (Tc) is found to decrease with increasing x. The large thermal hysteresis in magnetization under FC condition is noticed for x ⩽ 0.02, which is different in character for the composition range 0.05 ⩽ x ⩽ 0.15. The relaxation of magnetization indicates the ferromagnetic (FM) character for x = 0, while the coexistence of FM and glassy components is observed for x ⩾ 0.02. The glassy magnetic phase increases with the increase in Fe substitution. The inhomogeneous phase separation between FM and glassy magnetic phases has been proposed to explain the magnetic and electrical transport properties of La0.87Mn1−xFexO3.

Effect of A-site Fe substitution on the magnetic behavior of Dy2Ti2O7 spin ice

Effect of iron substitution in cryptomelane on the heterogeneous reaction with isoprene

Magnetic properties of Ni 75− xFe xAl 25 alloys: effect of site disorder

Structural and Mössbauer spectroscopic investigation of Fe substituted Ti–Ni shape memory alloys

Simultaneous Rietveld refinements of X-ray and neutron powder diffraction patterns were applied to study the effect of Fe substitution on the crystal structure properties of the Ca5−x Fe x (PO4)3OH system (0 ≤ x ≤ 0.3). From variations of the Ca(1) and Ca(2) site occupancies and modifications of interatomic distances with x, it is inferred that Fe substitutes at both crystallographic sites with a preference at the Ca(2) site. Such partiality is attributed to similar geometries of the sixfold coordinated Fe with the sevenfold coordinated Ca(2). The expected overall decrease of the lattice constants in the iron-substituted samples is followed by an increasing trend with x that is explained in terms of local lattice distortions. Hematite forms as a secondary phase starting at x = 0.1 up to 3.7 wt% for x = 0.3. Transmission electron microscopy reveals a nanosystem consisting of 15–65 nm rods and spheres, while hematite nanoparticles are distinguishable for x ≥ 0.1. A transition of the diamagnetic hydroxyapatite to paramagnetic Fe-hydroxyapatite was found from magnetic measurements, while the antiferromagnetic hematite develops hysteresis loops for x > 0.1.

Microstructure and mechanical properties of L12-strengthened Co–Ni–Fe-based superalloys

Enhancement of rotating magnetocaloric effect by Fe substitution in NdCo5-xFex alloys

Microstructure and hydrogen storage properties of Zr0.8Ti0.2Co1−xFex (x=0, 0.1, 0.2, 0.3) alloys

CoCr2O4 has attracted significant attention recently due to several interesting properties such as magnetostriction, magnetoelectricity etc. More recent experiments on Fe substituted CoCr2O4 observed a variety of novel phenomena such as the magnetic compensation accompanied by the occurrence of exchange bias, which reverses its sign. Understanding of such phenomena may lead to control the properties of these material in an efficient way to enhance its potential for multifunctional applications. In this paper, we study the fundamental understanding of Fe doping in modifying the structural and magnetic properties of CoCr2O4 with varying composition and substitution of Fe at different sublattices by first-principles density functional calculations. We have analysed in detail the effect of Fe substitution on crystal field and exchange splittings, magnetic moments and interatomic exchange parameters. It is also observed that with increasing concentration of Fe impurity, the system has a tendency towards forming an ‘inverse spinel’ structure as observed in experiments. Such tendencies are crucial to understand this system as it would lead to modifications in the magnetic exchange interactions associated with sites with different symmetry finally affecting the magnetic structure and the multiferrocity in turn.

The effects of Al and Fe substitution on the electrochemical performance of layered LiNi0.8-xCo0.2MxO2 (M= Fe, Al; x = 0.1) cathode materials were investigated. LiNi0.8-xCo0.2MxO2 (M= Fe, Al; x = 0.1) cathode materials were successfully synthesized by a combustion method with an annealing temperature of 700 °C for 24h. The physical and electrochemical properties of the materials were examined using X-ray Diffractometer (XRD), Field Emission Scanning Electron Microscopy (FESEM) and electrochemical charge-discharge. The XRD data showed that all the materials are single phase, hexagonal α-NaFeO2 type structure. The initial discharge capacity showed that Fe and Al substituted materials gave 39 % and 10 % improvement compared to the undoped LiNi0.8Co0.2O2 material. The discharge cycling also showed that the cycle stability has improved when Fe and Al was substituted. In view of electrochemical performance, Al containing sample was found to be better to those of LiNi0.8Co0.2O2 and Fe substituted cathode materials.

In In this study to understand the substitutional effect of Co-Zn on structural and magnetic properties of the BaFe12-2xCoxZnxO19 M-type hexagonal ferrites with concentration (x= 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized by the ceramic method. The results of x-ray diffraction show polycrystalline with single phase. Scanning electron microscopy micrographs shows the hexagonal ferrites that are composed of small particles with large porosity, roughly of spherical shapes. The substitution of Fe3+ ion by Co2+ and Zn2+ has changed magnetic properties of hexagonal ferrites.