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The impact of holmium (Ho) ions on lithium-rich spinel ferrites is studied through magnetic, morphological, and electrical transport properties. The X-ray photoelectron spectroscopy (XPS) analysis indicated the existence of all metal ions in the required valence state. Transmission electron microscopy (TEM) analysis exhibited nano-crystalline (∼50 nm) structures of these ferrites. The electrical resistivity measurements showed the higher resistivity values of the synthesized samples. The resistivity increased from 2.4 × 108 to 2.1 × 1010 Ω-cm with Ho inclusion, indicated an inverse relation with the size of grains. The Curie temperature (T c ) observed to decrease from 848 to 806 K with the incorporation of Ho 3+ ions. The activation energy (Δ E a ) noted to vary between 0.21 and 0.23 eV. The drift mobility (μ d) study revealed a decrease from 1.86x10 −12 to 6.14x10 −14 cm 2 V −1 s −1 by increasing Ho amount up to x = 0.06. A reduction in thermoelectric power (S) from - 143 to -95 μ.V/K by increase in Ho concentration confirmed the Fe replacement by Ho on octahedral B-sites. The ferromagnetic resonance (FMR) investigations indicated a drop in FMR line-broadening (ΔH) from 2491 to 2000 Oe by the increase of Ho concentration, making it beneficial to reduce microwave losses. A non-linear variation in the resonance field (H res) with the substitution of Ho was observed between 7359 to 7785 Oe. [ABSTRACT FROM AUTHOR]

Ho-substituted Li–Ni ferrites with composition L i 1.2 Ni 0.4 Ho x Fe 2- x O 4 ; 0≤ x ≤ 0.15 were synthesized by a self-ignited sol-gel process. An annealing temperature of 950 °C is estimated via thermal-gravimetric (TGA) analysis. X-ray diffraction (XRD) scans have confirmed the formation of the ferrite phase with a spinel structure in all samples. Substitution of Ho ions on the B-site significantly reduced the porosity from 38 -to 23% and the crystallite size from 23.4 -to 21.7 nm. Microstructural analysis revealed a denser structure with an increase in Ho content. Dielectric results showed that both the dielectric loss and dielectric constant depict a nonlinear variation with the addition of Ho. Complex impedance behavior with a single semicircle for all samples suggests the predominant effect of the grain boundary mechanism. The substitution of Ho ions in place of Fe ions significantly decreased the electrical conductivity. The anisotropic Ho3+ ions reinforce the L-S coupling which consequently enhanced the coercive force from 145 -to 389 Oe, and thus the anisotropy constant. [ABSTRACT FROM AUTHOR]

We investigate here the effect of holmium on Li–Co nano-ferrites to elaborate the surface morphology, dynamic magnetic and electrical transport properties. The transmission electron microscopy (TEM) technique was employed to examine the microstructure and grain size distribution. TEM analysis confirmed the nanocrystalline nature (~50 nm) of the prepared materials. X-ray photoelectron spectroscopy (XPS) experiment results verify the presence of all metal ions with the required valences. Ferromagnetic resonance (FMR) analysis revealed the need for a dense microstructure to cut down the microwave losses. FMR line width was observed to reduce from 2757 -to 1676 Oe except for x = 0.12 by the substitution of Ho ions which correspond to low microwave losses. The dc resistivity results show that high resistivity values are associated with smaller grains of the samples and vice versa. Resistivity values are found to increase from 3.66 × 108 -to 5.31 × 108 Ω-cm by increasing the Ho addition. Seebeck experiment revealed n-type conduction. Together with showing the nature of charge carriers, a decrease in the Seebeck coefficient with increasing Ho ensured the replacement of Fe ions by Ho ions on B-sites. [ABSTRACT FROM AUTHOR]

We report the dopant- and size-dependent variations in high-frequency magnetic and electrical transport properties of Ho-substituted Li-Mn polycrystalline ferrites. Thermal stability and phase identification were confirmed by thermal gravimetric analysis and X-ray diffraction experiments. The overall average crystallite size decreased from 29.6 to 17.5 nm, whereas the bulk density increased from 3.47 to 4.29 g/cm 3 with increasing Ho content. Ferromagnetic resonance (FMR) measurements at the X-band revealed significant shifts in FMR linewidths and resonance positions as a function of composition. Both, FMR linewidth and porosity, were found to decrease with the systematic addition of Ho from 2538 to 2359 Oe and from 26% to 15.4%, respectively. The substitution of Ho 3+ for Fe 3+ reduced the net magnetization of the spinel lattice from 53 to 41 emu/g. Electrical measurements revealed that the resistivity is higher in samples with smaller grains possessing a greater number of thin insulating grain boundaries. The activation energy ∆ E required for hopping increases from 0.09 to 0.16 eV with Ho addition, which may be well explained by the increase in resistivity. The substitution of Ho 3+ for Fe 3+ causes a decrease in Curie temperature T c due to the damping of A-B exchange interactions. [ABSTRACT FROM AUTHOR]

In the present study, the impact of holmium (Ho) substitution on structural, spectral, dielectric and magnetic behavior of Li 1.2 Zn 0.4 Ho x Fe 2−x O 4 (0.00 ≤ x ≤ 0.15) ferrites was investigated. The development of spinel phase and structural changes induced by Ho doping were confirmed by X-ray diffraction. The accommodation of Ho ions into spinel lattice was restricted for x ≥ 0.06 as indicated by ortho phase (HoFeO 3 ) traces. The decrease in lattice parameter ( a ) was attributed to the segregation of Ho ions on grain boundaries. FTIR spectra featured two intrinsic vibrational bands v 1 (617 cm −1 ) and v 2 (488 cm −1 ) for x = 0 due to tetrahedral and octahedral vibrations respectively. The compositional dependence of force constants and bond lengths has explained on the basis of cations distribution and oxygen-cation bond distances of respective sites. The addition of Ho ions decreased the saturation magnetization and optimized the coercivity from 59 to 335 Oe, proposing these ferrites for magnetic recording media. Dielectric results for the entire range of frequency (1 MHz to 3 GHz) revealed that ac conductivity increased from 3.5 × 10 5 to 1.8 × 10 6 (Ω-cm) −1 up to x = 0.09 and then it decreased slightly for x = 0.12. The effective contribution of grain-interior mechanism to dielectric behavior was confirmed by complex impedance study. The results of dielectric studies displayed that Ho doped lithium ferrites are suitable low loss potential materials for high frequency based applications. [ABSTRACT FROM AUTHOR]

A comprehensive study on structural, spectral, magnetic and dielectric properties of holmium substituted (Ho 3+ ) lithium ferrites; Li 1.2 Co 0.4 Ho x Fe 2−x O 4 (x = 0.00–0.15) synthesized via auto-citric combustion route has been carried out. The annealing temperature essential for complete decomposition of precipitates and spinel phase formation was found around 950 °C which was estimated from thermo-gravimetric analysis (TGA). The development of face centered cubic (FCC) spinel structure was confirmed from X-ray diffraction (XRD) analysis. However, the traces of an ortho phase (HoFeO 3 ) were appeared for x ≥ 0.06 indicating the solubility limit of Ho 3+ ions. The lattice constant ′ a′ increased from 8.351 to 8.360 Å upon Ho addition up to x = 0.06 and it decreased thereafter from 8.360 to 8.352 Å. This decrease in lattice constant was attributed to the secondary phase formation revealing segregation of Ho 3+ ions at grain boundaries. The porosity was found to decrease from 44 to 23% by the inclusion of Ho 3+ ions. Fourier transform infrared spectra (FTIR) exhibited tetrahedral ( v 1 ) and octahedral ( v 2 ) intrinsic vibrational bands at 627 cm −1 and 479 cm −1 respectively and these bands revealed a shift with increasing Ho concentration. The variations in force constants ( K o and K t ) were calculated and discussed with the tetrahedral (r A ) and octahedral (r B ) bond length trends. The dielectric parameters have been investigated as a function of composition and frequency. The systematic addition of Ho gradually increased the ac conductivity from 8.97 × 10 3 to 5.56 × 10 4 (Ω-cm) −1 up to x = 0.12 and it subsequently decreased for x = 0.15. The complex impedance examination (Cole-Cole plots) confirmed a grain-interior phenomenon, effectively contributing to the dielectric properties. The coercivity was enhanced while the saturation magnetization (Ms) was lessened by the incorporation of Ho 3+ ions. The maximum value of coercivity (706 Oe) was obtained for Li 1.2 Co 0.4 Ho 0.12 Fe 1.88 O 4 . The improved coercivity may suggest their utilization in perpendicular recording media applications. [ABSTRACT FROM AUTHOR]

We present the effects of size and oxygen defects on electrical and optical properties of nano crystalline bismuth ferrite (BiFeO 3 ) with rhombohedral symmetry synthesized by solution evaporation method. The effects of oxygen vacancies on the behavior of system have been studied by annealing all samples under two different environments, air and oxygen. Single phase crystal structure was confirmed by X-Ray diffraction (XRD). The crystalline size calculated by Scherrer's formula falls in the range of 11–21 nm for air and 20–29 nm in case of oxygen annealing atmosphere. The crystalline size was confirmed by Transmission electron microscope (TEM). Dielectric response reveals that both dielectric constant and dissipation factor (tanδ) decrease with increase of frequency without depicting any peak. Optical studies showed that the system possesses an indirect energy gap whose value increases with increasing particle size. There is an evidence for the presence of intra band states in this system arising from defect states. [ABSTRACT FROM AUTHOR]

Nano-sized Zr-Co doped nickel ferrites with nominal composition, NiZr x Co x Fe 2-2x O 4 ( x =0.0, 0.2, 0.4, 0.6, 0.8) were synthesized using the micro-emulsion route. The structural elucidation of the synthesized materials was carried out by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The XRD analysis confirmed face centered cubic (FCC) structure of all compositions of NiZr x Co x Fe 2-2x O 4 nanocrystallites. Crystallite size was calculated by Scherrer's formula found in the range 10–15 nm. The variation in lattice parameter as determined by XRD data agreed with size variation of host (Fe 3+ ) and guest (Zr 4+ and Co 2+ ) cations. FTIR spectra of doped NiFe 2 O 4 exhibited the typical octahedral bands at 528.4 cm −1 which is the characteristic feature of spinel structure of spinel ferrites. The characterized spinel NiZr x Co x Fe 2-2x O 4 nano-ferrites were evaluated for their potential applications by magnetic hysteresis loops and dielectric measurements. The value of saturation magnetization ( M s ) decreased from 47.9 to 13.09 emu/g up to x =0.8 with ups and downs fluctuations in between x=0.0 to x=0.8. The high values of Ms of some compositions predicted the potential applications in high density perpendicular recording media and microwave devices. The frequency dependent behavior of permittivity (ε') is recorded and discussed with the help of hopping mechanism of both holes and electrons. The dielectric and magnetic data of NiZr x Co x Fe 2-2x O 4 nano-ferrites suggested the potential applications of these ferrite nanoparticles in high frequency and magnetic data storage devices fabrication. [ABSTRACT FROM AUTHOR]

The plethora of properties associated with half Heusler compounds has made them apposite materials for functional applications significantly in thermoelectrics, solar harvesting, semiconducting and spintronics. The current study invested the exertions in unveiling the details of physical properties of LiXBe (X = N, P) compounds using DFT based VASP and WIEN2k codes considering PBE-GGA and TB-mBJ exchange correlation functionals. Titled compounds successfully assured the stability checks regarding energetic, lattice dynamic and mechanical. By means of electronic structure calculations, TB-mBJ functional disclosed the precise band gaps of 6.912 and 2.340 eV for LiNBe and LiPBe compounds respectively. Fat-band character analysis and partial charge density distributions in HOMO and LUMO orbitals revealed the governess of band edges around Fermi-level by homo-site (N- 2p & N- 2s) states in LiNBe and hetero-site (P- 2p & Li- 2s) states in LiPBe compound. The COHP examination and bond order characteristics evidenced comparatively strongest bonding interactions of X–Be than Li–Be bonding pair. The calculated opto-electronic properties; complex dielectric function, optical conductivity, loss function and refractive index have been discussed with substantial details. Physio-mechanical parameters and mechanical anisotropy have been comprehensibly elaborated. [Display omitted] • Investigation of Physical properties of LiXBe (X = N, P) compounds via DFT. • LiXBe (X = N, P) found structurally, lattice dynamically and mechanically stable. • TB-mBJ functional disclosed the precise bandgaps of LiXBe (X = N, P) compounds. • LiNBe compound propose bandgap engineering via solo-site substitution/doping. • LiPBe compound could be promoted for transparent conductor's applications. [ABSTRACT FROM AUTHOR]

In this work, Y 1 − x Pr x F e O 3 (0 ≤ x ≤ 0.16) ceramics were fabricated via the auto-combustion sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM) associated with EDS mapping, and Fourier transform infrared spectroscopy (FTIR) were employed for structural and morphology analysis. The substitution of praseodymium (Pr) modified the orthorhombic structure into a hexagonal structure. However, small traces of Fe 2 O 3 and Y 2 O 3 appeared in all samples. The lattice constant 'a' was increased from 3.523 to 5.530 Å upon substitution up-to x = 0.12, afterward this started to decrease from 5.530 to 5.529 Å. Pure orthorhombic YFeO 3 (o-YFeO 3) has cell volume 223.61 (Å3), while the cell volume of Pr substituted hexagonal YFeO 3 (h-YFeO 3) showed a decreasing trend (125.61–125.43 Å). Bulk density was thoroughly decreased from 5.009 to 4.634 (g/cm3) by increasing the Pr concentration. Frequency dependence of the dielectric behavior was investigated at room temperature in a comprehensive frequency range of 1 MHz ~ 3 GHz. SEM results exhibited the average grain size 149.28 nm, 66.78 nm, and 69.36 nm for the samples 0.00, 0.08, and 0.16, respectively. The identification of o-YFeO 3 was confirmed by two main absorption bands ν 1 (449.86 cm-1) and ν 2 (567.12 cm-1) and these bands indicate a clear shift upon the addition of Pr. The force constant of absorption bands at tetrahedral and octahedral sites showed increasing trend and this ranges from 1.633dyn/cm2x105 to 1.912dyn/cm2x105 and 2.818dyn/cm2x105 to 8.832dyn/cm2x105, respectively. The substitution of Pr significantly enhanced the dielectric constant. The shifting of peaks at higher frequencies demonstrates that an increase of dopant concentration resulted in the shifting of peaks that may follow the Maxwell-Wagner-Sillars polarization mechanism. Pr substituted YFeO 3 exhibited microwave frequency response in a range of 1.6 GHz–2.9 GHz which might be suitable for high-frequency applications. [ABSTRACT FROM AUTHOR]

Ni 0.5 Sn 0.5 Co x Mn x Fe 2−2x O 4 ferrites with x = 0.0–0.8 have been prepared by the micro-emulsion method, using CTAB as a surfactant material. X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and vibrational sample magnetometer (VSM) were used to investigate the effects of Co and Mn substitutions on cationic distribution, crystallite size, lattice constant, spectral, magnetic and dielectric properties. Lattice constant and crystallite size were found to increase from 7.4 to 9.25 Å and from 11.8 to 19.7 nm respectively with increasing substitution of Co and Mn ions. Saturation magnetization (M S ) gradually increased from 20.5 to 47.6 emu/g with increase in the value of x. However, Coercivity increased from 152.7 to 462.4 Oe up to x = 0.4 and then it decreased thereafter. The dielectric constant, complex dielectric constant and tan loss (tanδ) were observed to decrease with increase in frequency, depicting the semiconductor behavior of the ferrites. Dc resistivity was observed to decrease considerably upon addition of Co and Mn content. The outcome for the tunable magnetic properties and achieved modification of the synthesized nanocrystallites may be chosen for tremendous applications; such as miniaturized memory devices that are based on the energy storage principles and capacitive components. [ABSTRACT FROM AUTHOR]

A series of holmium (Ho) doped nanocrystalline Ni 0.7 Zn 0.3 Ho 2x Fe 2–2x O 4 ; 0.0≤x≤0.07 ferrite was synthesized using the conventional ceramic technique. The cubic spinel structure was confirmed by powder X-ray diffraction (XRD). The lattice parameter increases with increase in Ho content due to large ionic radius of Ho 3+ (0.901 Å) as compared to Fe 3+ (0.67 Å). Room temperature DC electrical resistivity and activation energy both increase with the increase of holmium contents. The saturation magnetization (M s ) decreased gradually from 78.92 to 54.17 emu/g due to holmium ions substitution in Ni-Zn ferrites. This decrease in M s is explained on the basis of redistribution of cations amongst the sites and weakening the A-B exchange interactions. An increase in electrical resistivity made this material suitable for its use in high frequency device applications. [ABSTRACT FROM AUTHOR]

Anti-perovskites have earned tremendous research interest in recent years, because of their copious unconventional physical, chemical and thermophysical properties. They are electronically inverted counterparts of perovskites' family and have become an emerging class of multifunctional materials, thus provides an enthusiastic and active research area to solid state scientists. Present work is devoted to explore some novel anti-perovskite materials using density functional theory based first-principles approach. The extant study includes the investigation of structural, electronic, elastic, mechanical, magnetic and thermophysical properties of XCNi 3 (X = Sc, Ti, V, Cr, Mn, Fe, Co and Cu) anti-perovskites. Structural and mechanical stability of studied compounds have been elaborated by computing formation energy and elastic constants respectively. The electronic properties of energetically and mechanically stable anti-perovskites have been found to be fully spin-polarized. Dependence of thermophysical properties under a broad range of temperature (0–1500 K) and pressure (0–100 GPa) have been discussed. Some of the anti-perovskites demonstrate intriguing properties and can be the potential candidates for magnetic applications e.g., magnetic sensors, spintronics, data storage devices and magnetic therapy. [Display omitted] • First-principles study of XCNi 3 (X = Sc, Ti, V, Cr, Mn, Fe, Co, Cu) anti-perovskites. • Computed formation energies preferred magnetic phase regarding structure stability. • Cauchy's pressure, Pugh's ratio and Poisson's ratio shown ductile nature of materials. • Spin-polarized band structures and density of states revealed the metallic features. • Thermophysical properties exhibited their dependence on temperature and pressure. [ABSTRACT FROM AUTHOR]

Dy–Ni substituted Mn 1-x Ni x Fe 2-y Dy y O 4 (x = 0.0–0.1 and y = 0.0–0.2) soft magnetic oxides were synthesized using a size controlled micro-emulsion method. X-ray diffraction (XRD) analysis was employed to confirm the spinel structure of synthesized ferrites. Crystallite size was found to decrease (33-22 nm) while lattice constant was increased (8.58–8.63 Å) by increasing dopants content. FTIR bands observed in the range 500–600 cm−1 is the evidence to form the spinel structure of these ferrites. Dielectric constant (ε′) and dielectric loss (ε") were observed to decrease with the increase of frequency due to hopping mechanism. Hysteresis curves exhibited soft nature of synthesized nanoferrites. Remanence (M R) and saturation magnetization (M S) were increased with the incorporation of Dy and Ni ions. The decreased in dielectric losses and increased in magnetic parameters suggested that these ferrites are potential candidates for magnetic recording heads. [ABSTRACT FROM AUTHOR]