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Ferromagnetic Co0.65Zn0.35Fe2O4 (CZFO) nanoparticles were sandwiched with bulk ferroelectric Ba0.7Sr0.3TiO3 (BSTO) material to study the magneto-electric coupling of composite system. In the present study, the CZFO nanoparticle is synthesized through sol–gel combustion and BSTO through solid-state reaction; followed by this, the composite system (1 − Φ) BSTO–ΦCZFO (Φ = 0.1, 0.2, and 0.3) was prepared by mixing according to weight percentage (Wt%) by solid-state reaction. The obtained XRD spectra of each CZFO, BSTO, and composites reflect the spinel cubic structure with space group Fd-3m, tetragonal structure with space group P4mm, and mixed index, respectively. Utilizing Rietveld refinement process, the structural parameters are extracted. The microstructural analysis by FESEM unveiled a high porous nature characterized by a thick-walled plant cell-like structure for all the composites. The magnetic hysteresis loops show the ferromagnetic nature of CZFO and composite samples. As the content of CZFO in the BSTO composite, the magnetic saturation increases with decrease in the coercive field values, which indicates that the ferromagnetic domain is controlled by ferroelectric domain. This is indirect evidence for existence of ME coupling. The room-temperature dielectric measurement suggest that as the CZFO content increased, their dielectric constant decreased and followed a trend of Maxwell–Wagner-type polarization as obeyed with Koop’s principle. Impedance study shows relaxation peaks, indicative of Debye-type polarization. The Cole–Cole plot is aligned with a semi-arc pattern and demonstrated a decrease in the radius of the semi arc as the CZFO content is mixed with BSTO and fitting well with the capacitance–resistance model. Significantly, the composition of Φ = 0.3 exhibited a ME voltage coefficient of 14.58 mV/cm Oe, which exceeded the values reported in previous research. This study reports the successful synthesis, and electrical, magnetic, and ME coupling parameters of CZFO–BSTO composites for potential applications. [ABSTRACT FROM AUTHOR]

Rare earth ion Nd+3 doped Co0.5Zn0.5−xNdxFe2O4 (x = 0.00 to 0.05) (CZNFO) nano-sized ferrite have been successfully constructed by self-ignited sol–gel method using citric acid (C6H8O7) as a chelating agent. The structural and morphology were satisfied by XRD patterns and FE-SEM microscopy, respectively. XRD spectra witnessed single phase without additional peaks, other than spinel type structure i.e., cubic structure with space group Fd-3 m as reported in JCPDS card No 22–1086. Rietvield refinement operation is done for gaining, lattice parameters, unit-cell volume and bond length. The evaluated crystallite sizes for CZNFO are 5–13 nm from Debye Scherrer equation, and additionally microstrain and dislocation density are estimated for pure and dopants. The inspection of cation distribution was done by the help of cation occupancy data. The morphology of grain is filament shaped and densely agglomerated with reducing of their grain size from 99.5 to 28 nm for each doping level, the reduced size impacts on the alteration of magnetic and electric properties. Extent to this, Fe–O bond and presence of tetrahedral (416 cm−1) and octahedral (570 cm−1) complexes were supported by FT-IR spectra, vibrating sample magnetometer executes a ferrimagnetic nature and downscale in the magnetic saturation as addition of Nd+3. Further, an applied frequency responses of dielectric constant and tan (δ) are significantly denote in higher frequency and firmly agree with Koop's and Maxwell Wagner theory of polarization. The non-Debye type of relaxation process is executed by impedance spectra study. Further the Cole–Cole fitted plot describes an approval of contribution of grain boundaries over grains with notable of semi-circle nature for each level of Nd dopant. Finally frequency dependent relative permeability at room temperature shows the decay in all doping composition and supports the good in electrical properties for rare earth ions. [ABSTRACT FROM AUTHOR]

Temperature‐dependent electronic and magnetic properties are reported for nickel‐deficient NiV2Se4. Single‐crystal X‐ray diffraction shows it to crystallize in the monoclinic Cr3S4 structure type with space group I2/m$I2/m$ and vacancies on the Ni site, resulting in the composition Ni0.85V2Se4 in agreement with our electron‐probe microanalysis. Structural distortions are not observed down to 1.5 K. Nevertheless, the electrical resistivity shows metallic behavior with a broad anomaly around 150–200 K that is also observed in the heat capacity data. This anomaly indicates a change of state of the material below 150 K. It is believed that this anomaly could be due to spin fluctuations or charge‐density‐wave fluctuations, where the lack of long‐range order is caused by vacancies at the Ni site of Ni0.85V2Se4. The non‐linear temperature dependence of the resistivity as well as an enhanced value of the Sommerfeld coefficient γ=104.0(1)$\gamma = 104.0\,(1)$ mJ mol−1 K−2 suggest strong electron–electron correlations in this material. First‐principles calculations performed for NiV2Se4, which are also applicable to Ni0.85V2Se4, classify this material as a topological metal with Z2=(1;110)$Z_2 = (1;110)$ and coexisting electron and hole pockets at the Fermi level. The phonon spectrum lacks any soft phonon mode, consistent with the absence of periodic lattice distortion in the present experiments. [ABSTRACT FROM AUTHOR]

We report the electronic properties of R4PtAl (R = Ho, and Er), which contains three sites for R, by the measurements of magnetization (ac and dc), heat-capacity, transport, and magnetoresistance (MR). Dc magnetization data reveal antiferromagnetic order below 19 K and 12 K in Ho and Er compounds, respectively. Additional features observed at lower temperatures (12 K for Ho4PtAl and 5 K for Er4PtAl) are akin to the cluster spin-glass phase. Resistivity data exhibit a weak minimum at a temperature marginally higher than their respective Néel temperature (TN), which is unusual for such rare-earths with well-localized 4f states. Isothermal magnetization and magnetoresistance data well below TN exhibit signatures of a subtle field-induced magnetic transition for a small magnetic field (<10 kOe). Notably, the isothermal entropy change at TN has the largest peak value within this rare-earth family; for a field change from zero to 50 kOe, the entropy change is ~14.5 J/kg K (Ho4PtAl) and ~21.5 J/kg K (Er4PtAl) suggesting a role of anisotropy of 4f orbital in determining this large value. The results provide some clues for the advancement of the field of magnetocaloric effect. The magnetocaloric property of Er4PtAl is nonhysteretic, meeting a challenge to find materials with reversible magnetocaloric effect. [ABSTRACT FROM AUTHOR]