Ferrimagnetic Behavior Research Articles

Correlation between structure, morphology and magnetic properties in ZnxCo0.8−xNi0.2Fe2O4 @SiO2 (0.1÷0.7) nanocomposites

The structure, morphology and magnetic properties of ZnxCo0.8−xNi0.4Fe2O4 @SiO2 (x = 0.1; 0.3; 0.5; 0.7) nanocomposites (NCs) were investigated. The formation of the ferrites and SiO2 matrix was confirmed by X-ray diffraction that indicated the presence of low-crystalline single-phase Ni-Zn-Co spinel ferrite at 500 °C, well-crystallized Ni-Zn-Co spinel ferrite accompanied by Fe2SiO4 at 800 °C and by crystalline SiO2 (tridymite and cristobalite) at 1100 °C. In NCs with high Zn2+ content annealed at 1100 °C, traces of α-Fe2O3 were also noticed. The average crystallite size increased from 9.56 to 38.0 nm with the increase of annealing temperature and decreased with the increase of Zn2+ content. The scanning electron microscopy revealed large aggregates of irregular shapes. The transmission electron microscopy revealed the presence of both small and large spherical particles with a tendency to form agglomerates. The increase of Zn2+ content led to an increase of the number of low-size particles. The investigated NCs with high Co2+ content annealed at 1100 °C displayed ferrimagnetic behavior, while those with high Zn2+ content exhibited superparamagnetic behavior. The magnetic properties (saturation magnetization, remanent magnetization, coercivity and anisotropy) evolved proportionally with the particle size and Co2+ content for the NCs annealed at 800 and 1100 °C, which is of high significance for possible applications in biomedicine as carriers for targeted drug delivery, hyperthermia treatment or magnetic resonance imaging agents.

Effect of Ho3+ on structural and magnetic properties of the Sm3-xHoxFe5O12 ceramic system

This work reports the effect of Ho3+ substitution and synthesis method on structural, morphological, and magnetic properties of the Sm3-xHoxFe5O12 (x = 0.0–1.0) produced by solid-state method and citrate reaction method. Structural characterization showed the suitable insertion of Ho3+ into dodecahedral sites, favoring the formation of the cubic structure and space-group Ia-3d (230). Obtained materials exhibited particle sizes less than 1.0 µm and of up to 4.5 µm for the samples obtained by the citrate and the solid-state reaction method. On the other hand, the magnetic analysis showed a ferrimagnetic behavior in the materials, which is attributable to the difference between the magnetic moments of Sm3+ and Ho3+. Thus, Ho3+ insertion in the host structure led to decreasing in the saturation magnetization and increasing in the coercive field. These results showed that Ho3+ insertion in the Sm3Fe5O12 ceramic allows its potential applications in antennas and high-frequency devices.

Impact of the R and Mg on the structural, hydrogenation and magnetic properties of R3-Mg Co9 (R = Pr, Nd, Tb and Y) compounds

R2MgCo9 (R = Pr, Nd, Tb and Y) compounds have been synthesized by a powder sintering method and the corresponding hydrides have been prepared by a solid gas method. Their crystal structures and magnetic properties have been systematically studied. X-ray diffraction analysis showed that all R2MgCo9 compounds belong to the PuNi3-type structure. The elements Tb, Y, Nd, Pr yield a lowering of the equilibrium pressure which correlates well with the increase in cell volume. The R2MgCo9H(D)x (R = Pr, Nd, Tb and Y; (9.4 ≤ x ≤ 12)) hydrides (deuterides) preserve the PuNi3-type structure with hydrogenation-induced volume expansion ranging from 14.7 to 19.6%. The substitution of deuterium for hydrogen in R2MgCo9–(H,D)2 (R = Tb and Y) prevents fast desorption at room temperature and ambient pressure. As for the magnetic properties, all the studied intermetallic compounds show ferromagnetic or ferrimagnetic behavior, and in some cases a temperature dependent spin reorientation. Hydrogen insertion reduces the magnetization and decreases the magnetic ordering temperature (TC), whereas Mg for R substitution increases TC.

Magnetically responsive chitosan-pectin films incorporating Fe3O4 nanoparticles with enhanced antimicrobial activity

Chitosan-pectin films with iron oxide (Fe3O4) magnetic nanoparticles were prepared by solution casting in order to produce biopolymer based magnetically active materials. Infrared (FTIR) spectra indicated physical interactions between the matrix and nanoparticles, corroborated by differential scanning calorimetry (DSC) results. In addition, thermal characterization suggested that the interactions between chitosan, pectin and the nanoparticles resulted in a less compact structure, influencing the film mechanical properties. Regarding vibrating-sample magnetometry (VSM) and electrical analysis, chitosan-pectin films with Fe3O4 nanoparticles showed ferrimagnetic behavior, with an increase of the dielectric constant as the nanoparticle concentration increased. Furthermore, films displayed enhanced antimicrobial activity against Escherichia coli (Gram-negative) and Staphylococcus epidermidis (Gram-positive) bacteria. Therefore, chitosan-pectin films with Fe3O4 magnetic nanoparticles provide promising results for active and intelligent food packaging applications.

Experimental and theoretical investigation of FeCrVAl and related compounds

We have carried out a combined theoretical and experimental investigation of FeCrVAl, and the effect of Mn and Co doping on its structural, magnetic, and electronic band properties. Our first principles calculations indicate that FeCrVAl, FeCr0.5Mn0.5VAl, and FeCr0.5Co0.5VAl exhibit nearly perfect spin polarization, which may be further enhanced by mechanical strain. At the same time, FeCrV0.5Mn0.5Al and FeCrV0.5Co0.5Al exhibit a relatively small value of spin polarization, making them less attractive for practical applications. Using arc melting and high vacuum annealing, we synthesized three compounds FeCrVAl, FeCr0.5Mn0.5VAl, and FeCr0.5Co0.5VAl, which are predicted to exhibit high spin polarization. The room temperature x-ray diffraction patterns of all samples are fitted with full B2 type disorder with a small amount of FeO2 secondary phase. All samples show very small saturation magnetizations at room temperature. The thermomagnetic curves M(T) of FeCrVAl and FeCr0.5Co0.5VAl are similar to that of a paramagnetic material, whereas that of FeCr0.5Mn0.5VAl indicates ferrimagnetic behavior with the Curie temperature of 135 K. Our findings may be of interest for researchers working on Heusler compounds for spin-based electronic applications.

Structural, morphological and magnetic properties of hexaferrite BaCo2Fe16O27 nanoparticles and their efficient lead removal from water

W-hexaferrite BaCo2Fe16O27 was prepared using the citrate nitrate combustion method. The sample was characterized using XRD, SEM, EDX and elemental mapping. XRD confirmed that the sample was synthesized in a single phase hexagonal structure with an average crystallite size 37.39 nm. SEM images of the sample show a spongy morphology with the agglomerated grain owing to dipole interaction between the crystallites. The magnetic properties of BaCo2Fe16O27 were studied using H-M hysteresis loop and the DC magnetic susceptibility. The sample has a ferrimagnetic behavior with saturation magnetization 64.133 emu/g. The magnetic properties of BaCo2Fe16O27 are originated from the Fe3+–O–Fe3+ superexchange. The synthesized sample is used as an adsorbent to remove the heavy metal Pb2+ from water. BaCo2Fe16O27 has Pb2+ removal efficiency 99% and 28% at pH 8 and 7 respectively. The Langmuir and Freundlich isotherms were used to analyze the experimental data. The Freundlich adsorption isotherm fitted the experimental data well.

Emergence of robust half-metallic spin gap and a sizeable magnetic anisotropy in electron-doped Ca[formula omitted]FeOsO[formula omitted

Half-metallic materials having a large band gap (Eg) along with giant magnetocrystalline anisotropy energy (MAE) have been proposed to be crucial for the development of magnetic tunnel junctions. Herein, electron-doped Ca2FeOsO6 (CFOO) double perovskite oxide is investigated by employing ab-initio calculations with the inclusion of Hubbard U and spin–orbit coupling effects. Electron doping is realized by introducing Co+2/Ni+2 ion with 3d7 (t2g3↑t2g2↓eg2↑eg0↓)/3d8 (t2g3↑t2g3↓eg2↑eg0↓) configuration at Fe+33d5 (t2g3↑t2g0↓eg2↑eg0↓) site. The thermodynamical, mechanical, and dynamical stability of these motifs for determining the synthesis feasibility at ambient conditions is established by calculating the formation energetics, elastic constants, and phonon band structure, respectively. The undoped CFOO system displays a ferrimagnetic Mott-insulating behavior due to a strong antiferromagnetic coupling between Fe and Os ions. On the other hand, electron doping induces half metallicity in CFOO, where extra electrons provided by TM-dopants produce a repulsion in the partially filled Os t2g3↓ spin-minority channel. As a consequence, the Os bands near the Fermi level are shifted to higher energetics; resulting in a conducting nature for the doped motifs. Therefore, Os ion remains in the mixed formal valence states of Os+5 and Os+6/Os+7, which reduces the moments as well. Most remarkably, a large Eg of 1.26/1.65 eV exists in the spin-majority channel of Co/Ni-doped structure, which is highly desired to effectively suppress the spin-flipping and affirm the large mean free path for spins along with a high spin-filtering response. Our results also demonstrated that the half metallicity of the studied TM-doped CFOO is robust and can be preserved under a reasonable magnitude of biaxial strains ([110]). Additionally, a sizeable MAE constant of ∼×107 erg/cm3 indicates that these materials could be potential candidates for the data storage devices.

Comparison of Structural, dielectric and magnetic investigation of Cr3+ substituted Mg-Cu, Mg-Zn, and Mg-Ni ferrites system

• Studied the effect of Cr 3+ substitution on the structural, dielectric, and magnetic properties of Mg 0.5 M 0.5 Fe 1.5 Cr 0.5 O 4 (M = Cu, Zn, and Ni) ferrite system prepared by sol–gel method. • The XRD patterns showed a single spinel phase. • The magnetic saturation (M s ), magnetic moment (M r ), and Coercivity (H c ) is found to be the highest for the Cr substituted Mg-Ni ferrite system. • All the synthesized samples showed ferrimagnetic behavior. • Thus, the magnetic and structural properties of (Mg 0.5 M 0.5 Fe 1.5 Cr 0.5 O 4 (M = Cu, Zn, and Ni) NPs can be favorable for their potential use in high-density recording media applications. Effect of Cr 3+ substitution on the structural, dielectric, and magnetic properties of Mg 0.5 M 0.5 Fe 1.5 Cr 0.5 O 4 (M = Cu, Zn, and Ni) ferrite system prepared by sol–gel method. All ferrites prepared samples’ powder; X-ray diffraction patterns confirmed the formation of single-phase cubic spinel structures with Fd -3 m space group. It possesses a monophasic cubic-spinel lattice structure with an average crystallite size ranging from 25 to 44 nm. The lattice constant determined by XRD analysis falls between 8.497 Å and 8.392 Å. Furthermore, the crystallite size determined by XRD data is well matched with the particle size determined by scanning electron microscopy images. Using an LCR Meter, the dielectric parameters of the samples, such as dielectric constant ( ε ’) and dielectric loss tangent (tan δ ), were studied as a function of frequency in the range of 100 Hz to 5 MHz at room temperature. The dielectric constant and loss tangent among the samples show a normal dielectric behavior with a frequency which reveals that the dispersion is a result of the Maxwell-Wagner type interfacial polarization and hopping of electrons between the Fe 2+ and Fe 3+ ions. The hysteresis curve exhibits the particles are soft ferrimagnetic with maximum saturation magnetization, Ms = 38.55 emu/g due to Cr substituted Mg-Ni ferrite. The squareness ratios were discovered to be less than 0.5, indicating that our particles have a single-domain ferrimagnetic isotropic nature. Thus, the magnetic and structural properties of (Mg 0.5 M 0.5 Fe 1.5 Cr 0.5 O 4 (M = Cu, Zn, and Ni) NPs can be favorable for their potential use in high-density recording media applications.

Ferrimagnetic behavior in a naphthalene templated manganese(II) 1,1-cyclohexanediacetate compound

A new manganese(II) 1,1-cyclohexanediacetate compound of formula [Mn13(chda)12(H2O)4(OH)2]n·n(nap) [H2chda = 1,1-cyclohexanediacetic acid, nap = naphthalene] has been synthesized by a hydrothermal reaction and characterized through single crystal X-ray synchrotron diffraction, exhibiting a 3D architecture, where the nap molecules are weakly anchored in the cavities of the [Mn13(chda)12(H2O)4(OH)2]n coordination polymer through steric interactions. Magnetic analysis reveals a long-range ferrimagnetic order below 2.4 K, most likely due to non-compensation of the magnetic moments. The non-compensation in spin moments arises, for topological reasons, from the network of exchange couplings associated to the binding modes (carboxylate and µ-oxo). This compound is one of the few examples of homometallic topological ferrimagnets built up from carboxylate ligands.

Role of neodymium substitution on the structural, magnetic and microwave absorbing properties of nickel ferrites

The neodymium substituted nickel ferrites with a nominal composition of NiNdxFe(2-x)O4 (with x = 0.00; 0.01; 0.03; 0.05; 0.06; 0.08 and 0.10) were successfully synthesized by milling technique. The NiO, Nd2O3 and Fe2O3 powders were used as raw materials and were prepared in a mole ratio. The characterization of the samples was done by X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA). In this study, the PXRD showed and verified that all Nd3+ ion successfully substituted the NiFe2O4 samples with a single cubic spinel phase. Infrared spectra showed two strong absorption bands in the frequency range of 405–420 cm−1 and 595–610 cm−1, which were respectively attributed to tetrahedral and octahedral sites of the spinel ferrites. The SEM revealed homogenous morphology on all NiNdxFe(2-x)O4 but still not uniform powders. The particle size of the powder ranged from 150 to 700 nm. The magnetic properties of all of the samples showed a ferrimagnetic behavior. The Ms value was decreased when the Hc increased with increases in the Nd3+ substitution value. The ability to absorb the microwave measured by VNA shows the enhancement of the microwave attenuation where the Nd3+ substitution increased. The microwave attenuation changes increased from 91.25% to 98.32%. It can be seen that the composition of x at 0.05 promises to be new material for microwave absorption.

Co-precipitation of zinc ferrite nanoparticles in the presence and absence of polyvinyl alcohol with other constant parameters and the analysis of polyvinyl alcohol mediated zinc ferrite nanoparticles

In the present study, a less explored morphology controlling synthesis technique – coprecipitation was used in the synthesis of zinc ferrite nanoparticles. Zinc ferrite nanoparticles were synthesized in the presence and absence polyvinyl alcohol (PVA) mediation by maintaining the other parameters constant. The crystallite size, determined by X-ray diffraction technique was greater for PVA mediated zinc ferrite (67 nm) compared to the zinc ferrite synthesized in the absence of PVA (52 nm). The morphology of the samples was analyzed using scanning electron microscopy technique. The use of PVA as surfactant resulted in reduced agglomeration, refined morphology, smaller particle size and hence high surface to volume ratio of the zinc ferrite nanoparticles. The PVA mediated zinc ferrite was further characterized. The optical, magnetic, photocatalytic and antibacterial properties of the sample were determined. The sample had a narrow optical bandgap energy of 1.98 eV. It exhibited ferrimagnetic behaviour suggesting the formation of mixed spinel structured zinc ferrite with zinc and oxygen vacancies. Photocatalytic efficiency of the sample was determined by degrading methylene blue in the presence of sunlight and halogen lamp. The antibacterial activity of the sample was studied against Escherichia coli and Staphylococcus aureus.

Syntheses and magnetic properties of substituted bis-indacenyl bi-metallic complexes & application

Organometallic compounds, Bis (2,4,6,8 teramethyl-indacenyl) di Iron (1), Bis (2,4,6,8 teramethyl s-indacenyl) mono iron, mono cobalt (2), and Bis (2,6 diethyl-4,8-dimethyl-s-indacenyl) di cobalt (3) were synthesised by means of salt elimination strategy, using Fe(II) and Co(II) salts. The compounds were characterised through spectroscopic and electrochemical methods. Magnetic measurements were carried out by Physical Property Measurement System (PPMS). Mossbauer spectroscopic data reveals that in all compounds, surprisingly, Iron is in +3 oxidation state. DFT calculations have been carried out to understand the change in the oxidation state of a metal. DFT study confirms the electron transfer nature of ligand to metal. Cyclic voltametric study on these compounds shows a large separation (ΔE>800mV) between two oxidation peaks confirming the strong interaction between the metal centres. Magnetic measurements on these organometallic compounds reveals that they exhibit a ferrimagnetic behaviour at temperatures below 40 K.

Effect of single and mixed Bi, Ga doping on the magnetic properties of Y3Fe5O12

The stability, structural, magnetic, and band structure properties of Y3Fe5O12, Y2.75Bi0.25Fe5O12, Y3Fe4GaO12, and Y2.75Bi0.25Fe4GaO12 solid solutions were studied by first-principles calculations. The results demonstrated that the substitution of Bi3+ induces a reduction in the bandgap of Y3Fe5O12. At the same time, Ga3+ was introduced in both the octahedral and tetrahedral sites of Fe3+ and it was found that the bandgap remained almost unchanged. On the other hand, the magnetization was reduced with the incorporation of Bi3+, coinciding with the experimental trend observed in the literature while increasing with Ga3+ incorporation. This behavior is attributed to the disruption of the magnetic sublattices. These results help to understand the ferrimagnetic behavior of YIG and encourage its use as a promising material for optoelectronic and spintronic applications. It is also shown that there is a margin for manipulating the magnetic response through appropriate doping.

Bi3+ and V3+ co-substituted Ni-Co spinel ferrites: Synthesis, optical, magnetic characterization and hyperfine interaction

Ni0.5Co0.5VxBixFe2-2xO4 spinel ferrite nanoparticles with composition (x = 0.00, 0.02, 0.04, 0.06 and 0.08) (CoNiVBiFeO (x = 0.00–0.08) SFNPs) were well fabricated hydrothermally. The consequence of co-substitution of both Bi3+ and V3+ ions on structure, morphology, and magnetic features of Ni0.5Co0.5Fe2O4 SFNPs were studied using XRD (X-ray diffractometry), scanning (SEM) and transmission (TEM) electron microscopies along with EDX, XPS (X-ray photoelectron spectroscopy), VSM (vibrating sample magnetometry) and Mossbauer spectroscopic techniques. The pure spinel ferrite (SFs) phase was approved via XRD. The morphology of SFNPs were revealed by SEM and TEM. Hyperfine parameters are determined from fitting room temperature Mössbauer spectra. The V3+ and Bi3+ ions occupy mainly at B site. The isomer shift values are coupled with the characteristics of the high spin Fe3+ ion. The influence of V3+ and Bi3+ ions co-doping on the magnetic features of Ni-Co SFNPs has been also investigated at 300 and 10 K. The saturation magnetization (Ms), remanence (Mr), coercive field (Hc), and Bohr magneton number (nB) are extracted from the recorded M-H hysteresis loops. Nanomagnetic materials with x content of 0.02, 0.08, and 0.10 exhibited superparamagnetic (SPM) behavior, whereas other products with x content of 0.00, 0.04, and 0.06 displayed soft ferrimagnetic behavior at ambient temperature. The different prepared nanoferrites displayed hard ferrimagnetic characteristic at 10 K. The Ms and Mr values are decreased as result of V3+ and Bi3+ ions co-doping. However, Hc does not show a monotonic trend. The fluctuations in magnetic moments of ions, super-exchange coupling, and distribution of cations are correlated with the changes in magnetic parameters to explain their variations.

Effect of Nickel Substitution on Structural and Magnetic Properties of Novel Polyol route Synthesized Cobalt Ferrite

Nanocrystalline NixCo1-xFe2O4 (1.0 ≥ x ≥ 0) ferrites were prepared by polyol route. Formation of single phase cubic spinel structure for all the compositions was confirmed from their X-ray diffraction patterns. These ferrite samples existed as crystalline nanoparticles of about 10-20 nm size as observed from Transmission Electron Microscopy technique. The magnetic studies indicated that, the ferrimagnetic behavior increases with nickel substitution.

Impact of sonication time on the structural and magnetic features of CoFe2O4/Ni0.8Cu0.1Zn0.1Fe2O4 hard-soft nanocomposites

Hard/soft (H/S) CoFe2O4/Ni0.8Cu0.1Zn0.1Fe2O4 nanocomposites (NCs) were prepared via ultrasonic irradiation method under different ultrasonication durations (10, 20, 30, 40, 50, and 60 min). The structure and morphology of these nanocomposites were analyzed through XRD, FT-IR, SEM, TEM, and EDX techniques, which confirmed the successful preparation of the desired nanocomposites. The crystallites/particles size was found to reduce with increasing ultrasonication duration. The magnetic properties of H/S CoFe2O4/Ni0.8Cu0.1Zn0.1Fe2O4 NCs prepared via ultrasonication method under different ultrasonication durations (10, 20, 30, 40, 50, and 60 min) were investigated through measurements of magnetization against the magnetic field (M-H) at 10 and 300 K. The soft character of the prepared NCs at room temperature depicted their superparamagnetic behaviors. At extremely low temperatures (T = 10 K), all H/S ferrite NCs revealed opened M-H hysteresis loops, indicating their ferrimagnetic behavior at low temperatures. All H/S NCs do not reveal any kind of anomalies in their M-H curves. Additionally, the SFD (switching field distribution) analysis pointed out a single peak in dM/dH against H curves. It was found that the intergranular exchange coupling interactions are more dominant than the intergranular dipolar interactions. Such a result indicates that the current synthesis method is useful to produce good exchange-coupled hard/soft ferrite NCs. It was also observed that the Ms and Mr values at both 10 and 300 K are decreasing with rising the ultrasonication duration. However, the Hc value was found to increase with rising ultrasonication duration, reaching a maximum value under an ultrasonication duration of 30 min, then, the Hc value decreases with further rising the ultrasonication duration. The plausible reasons for the variations in magnetic parameters were discussed.

Structural spectral, dielectric, and magnetic properties of Mg substituted Ba3CoFe24O41 Z-type hexaferrites

The Ba3Co2-xMgxFe24O41 hexaferrites were prepared by the sol–gel combustion route. The materials were annealed at 1350 °C and displayed the single-phase characteristics. X-ray density (Dx) decreases owing to increasing Mg-concentration. Crystallite size was calculated with the help of Debye Scherrer's formula and found within the 17–18 nm range. Fourier transform infrared spectroscopy was used to determine the specific absorption peaks of hexagonal ferrites. It was executed in the region of 420–700 cm−1—the occupancy of Mg2+ ions at the octahedral site at delayed alternation of Fe3+ ions. As a result, the dielectric permittivity decreased. The grain boundary contribution was clearly seen in synthesized ferrites' cole plots. The cole – cole plots show a single semi-circle which reveals that grain boundaries play a significant role in the conduction process. Magnetic measurement indicated the ferrimagnetic behavior of all samples.

Facile Synthesis, Characterization, Catalytic and Photocatalytic Activity of Multiferroic BiFeO3 Perovskite Nanoparticles

We report the synthesis of multiferroic BiFeO3 perovskite nanoparticles using the microwave combustion technique. Phase evolution is investigated by XRD, which confirms that the formation of a secondary α-Bi2O3 phase with a monoclinic structure along with the existing rhombohedral (BiFeO3) structure. The average crystalline size has been found at 50 nm. The optical band gap was calculated from the Tauc’s plot it has been found 2.18 eV. The appearances of FT-IR spectra revealed bands at 550 and 444 cm−1 were correlated to the rhombohedral stretching modes of BiFeO3 nanostructure. The surface morphology showed the formation of nanosized grains with pores. The magnetization-Field (M-H) hysteresis curves revealed the appearance of ferrimagnetic behavior at room temperature. The BET surface area of BiFeO3 perovskite nanoparticles was found 44.86 m2/g. The as-fabricated BiFeO3 perovskite nanoparticles were investigated for their superior catalytic activity in two applications, which include (i) Glycerol to formic acid oxidation in the liquid phase with a high efficiency of over 98 percent, (ii) Under visible light, the photocatalytic breakdown of rhodamine B achieved maximal efficiency (almost 99 percent). Finally, we concluded that the BiFeO3 perovskite nanoparticles exhibit high performance in future multifunctional devices is demonstrated by the simultaneous enhancement of catalytic and photocatalytic activities.

Structural, electronic and magnetic properties of inverse spinel NiFe2O4: DFT + U investigation

We have used ab initio density functional theory (DFT) to explore the structural, mechanical, electronic and magnetic properties of inverse spinel NiFe2O4. The ultra-soft pseudopotential method parametrized under generalized gradient approximation (GGA) for the exchange-correlation functional with Hubbard correction (GGA + U) was applied. The equilibrium lattice parameter was estimated to be 8.4620 Å and the 3 independent elastic constants C11, C12 and C44 were found to be 304.12 GPa, 144.45 GPa and 57.46 GPa, respectively. GGA + U formalism could successfully explain the semiconducting and ferrimagnetic behaviour of NiFe2O4. The spin-polarized electronic density of states reveals that the p−d hybridization between O and Fe atoms is responsible for the semiconducting nature of NiFe2O4. The ferrimagnetic behaviour of inverse spinel NiFe2O4 can be explained through the anti-parallel spin configuration of tetrahedrally and octahedrally occupied Fe atoms. The resultant magnetic moment is thus solely contributed by the octahedrally occupied Ni atoms. Spin-polarized band structure calculations reveal indirect band gap of 1.6 eV for spin-up channel and direct band gap of 2.2 eV for spin-down channel.

Structural, electronic and magnetic properties of La1.5Ca0.5(Co0.5Fe0.5)IrO6 double perovskite

In this work, we report the synthesis and investigation of structural, electronic, and magnetic properties of La1.5Ca0.5(Co0.5Fe0.5)IrO6. Our polycrystalline sample forms as a single-phase double perovskite in monoclinic P21/n space group. Co and Ir are most likely in bivalent and tetravalent oxidation states, respectively, while Mössbauer spectroscopy indicates that Fe is in a trivalent state. The ac and dc magnetization data suggest a ferrimagnetic behavior resulting from the presence of two antiferromagnetic sublattices at Co/Fe and Ir sites. The large coercive field HC≃ 32 kOe observed at 10 K, comparable to that of other double perovskites of interest for hard magnets, is discussed in terms of the structural distortion and the spin and orbital magnetic moments of the transition metal ions.