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Currently, semiconductor–relaxor ferroelectric (0–3) type composites are promising lead-free ferroelectric candidates for high-temperature piezoelectric applications. Among all, 0.30(ZnO)-0.70[(Bi0.5Na0.5)0.94Ba0.06TiO3] is one of the most studied composites by researchers. Therefore, to understand the role of ZnO on the polarization reversal process and domain states of (Bi0.5Na0.5)0.94Ba0.06TiO3, the dynamic ferroelectric hysteresis of the present composite has been investigated as a function of electric field amplitude (E0) and frequency (f). According to the power law, a set of scaling relations between the loop area ⟨A⟩ with E0 and f have been established for minor and saturated loops, which take the form of ⟨ A ⟩ ∝ f − 0.389 E 0 4.586 and ⟨ A ⟩ ∝ f − 0.021 E 0 1.066 , respectively. Also, it is interesting to note that the frequency-dependent ferroelectric hysteresis loops [for the saturated field (E0) = 50 kV/cm] exhibit the unique two-stage scaling behavior. Additionally, the origin of enhancement in the domain switching process for minor loop regions has been correlated with the presence of a semiconductor (ZnO), which is extensively discussed in the present study. [ABSTRACT FROM AUTHOR]

Composites of barium hexaferrite (BaFe 12 O 19) and nickel zinc ferrite (Ni 0.5 Zn 0.5 Fe 2 O 4) have been prepared by the high-energy planetary ball mill method. The magnetic composites are characterized by employing X-ray Diffraction and High-Resolution Transmission Electron Microscopy (HRTEM) techniques. The percentage of barium hexaferrite (BaFe 12 O 19) and nickel zinc ferrite (Ni 0.5 Zn 0.5 Fe 2 O 4) in the composite has been obtained from the Rietveld analysis of XRD patterns. The average crystallite sizes of BHF and NZFO are found to be comparable in the composites. The magnetic properties of (1-x) BHF-(x) NZFO with x = 0 to 1 have been studied by measuring the magnetic hysteresis loop (M-H loop) for all the samples. The M-H loops are analyzed by plotting the loop width (ΔH) versus magnetization (M). The magnetic hysteresis loops for the BHF and NZFO are found to be symmetric in all the quadrants. However, symmetry breaks in M-H loops for composites. The symmetry breaking in magnetic hysteresis loops of the bi-magnetic composite suggests a new approach to analyzing the magnetic interaction between magnetic phases in the magnetic composites. [ABSTRACT FROM AUTHOR]

In view of tuning different transitions, Co and V are substituted in Mn-rich Ni-Mn-Ga alloy. Ni41Co9Mn30V2Ga18 sample undergoes a coupled magnetostructural transition above room temperature with a low thermal and magnetic hysteresis and high sensitivity of martensite transition temperature (8 K/T) with the field. ∆SM is found to be a maximum of −2.33 J/kg-K for 3 T field change with a large RCP of 158 J/kg. The presence of intermartensite transition along with the magnetostructural transition widens the range of working temperature. [ABSTRACT FROM AUTHOR]

This paper reports on reduced graphene oxide (rGO), tin oxide (SnO2) and polyvinylidene fluoride (PVDF) tertiary nanocomposite thick film based flexible gas sensor. The nanocomposite of 0.90(PVDF) − 0.10[x(SnO2) − (1 − x)rGO] with different weight percentages (x = 0, 0.15, 0.30, 0.45, 0.6, 0.75, 0.90 and 1) have been prepared by the hot press method. Chromium (Cr) has been deposited on the surface by using E-beam evaporation system, which is used as electrode of the device. Crystal structure, morphology, and electrical characteristics of the device have been explored for the technological application. A correlation between crystallinity, morphology, and electrical properties with these thick films has also been established. The device has been tested at different hydrogen (H2) gas concentration as well as at different response times. A superior response of 0.90(PVDF) − 0.10[0.75(SnO2) − 0.25 rGO] nanocomposite thick film has been observed. Hence, this composition is considered as optimized tertiary nanocomposite for the hydrogen gas sensor application. The sensor response of 49.2 and 71.4% with response time 34 sec and 52 sec for 100 PPM and 1000 PPM H2 gas concentration respectively have been obtained. First time a new kind of low cost and flexible polymer based nanocomposite thick film gas sensor has been explored. [ABSTRACT FROM AUTHOR]

An interfacial integration at the nanoscale domain through a core@shell (CS) nanostructure has constructively unbarred a wide dimension to researchers on biomedical applications, especially for magnetic fluid hyperthermia. Lately, the interconnection of the exchange bias effect (EBE) through the interface coupling to the magnetic heating efficiency has uttered its utmost prominence for researchers. Here, we delineate the ascendency of the heating ability through a coalescing assembly of mixed ferrite Co0.5Zn0.5 Fe2O4 (CZ) and soft magnetic material Fe3O4 (F), by devising a network of CoZnFe2O4@Fe3O4 (CZF) CS nanostructure. A hefty interface activity with validation of the EBE phenomenon is divulged through magnetic scrutiny for the CS sample. The magnetic nanoparticles heating response to applied magnetic field and frequency is discerned at three distinct fields, where the outcome prevailed to inflated specific loss power for CS CZF in distinction to bare F and CZ samples for all the assessments. Remarkably; a lofty intrinsic loss parameter is also perceived for the CS sample recorded to about 5.36 nHm2 g−1; which is another eccentric outcome that significantly labels the CS CZF sample as a potentially high heating competence agent. This comprehension accords to a finer perspective to meliorate the theranostic environment for hyperthermia applications. [ABSTRACT FROM AUTHOR]

The advancement of magnetic materials with coupled magneto-structural phase transition (MST) to fulfill the ultimate objectives of practical solid-state cooling applications requires a better understanding of the hysteresis phenomenon linked across the phase transition region along with the large magnetocaloric parameters. For the present sample Mn0.65Ni0.65Fe0.70Si, the MST is associated with a sharp jump in magnetization along with a small thermal hysteresis of ∼13 K. A giant isothermal magnetic entropy change (| Δ S M max |) of ∼37.6 J kg−1 K−1 at 299 K and effective refrigerant capacity (R C effe ) of ∼214.3 J kg−1 under ΔH = 30 kOe is obtained with excellent compatibility between the martensite and austenite phases. The geometrical compatibility condition, i.e., very small (∼0.55%) deviation of the middle eigenvalue (λ 2) from unity justifies the observation of small hysteresis in the present material. The investigation of hysteresis behavior under different extents of the driving forces (temperature or magnetic field) reveals that both the driving forces trigger equally the phase transition and are responsible equivalently for the hysteresis phenomenon. The present study provides a pathway to understand the complexity of the hysteresis behavior, its impact on the reversibility of magnetocaloric effect, and its minimization by optimizing the geometrical compatibility condition between the austenite and martensite phases. [ABSTRACT FROM AUTHOR]

An interfacial integration at the nanoscale domain through a core@shell (CS) nanostructure has constructively unbarred a wide dimension to researchers on biomedical applications, especially for magnetic fluid hyperthermia. Lately, the interconnection of the exchange bias effect (EBE) through the interface coupling to the magnetic heating efficiency has uttered its utmost prominence for researchers. Here, we delineate the ascendency of the heating ability through a coalescing assembly of mixed ferrite Co0.5Zn0.5 Fe2O4 (CZ) and soft magnetic material Fe3O4 (F), by devising a network of CoZnFe2O4@Fe3O4 (CZF) CS nanostructure. A hefty interface activity with validation of the EBE phenomenon is divulged through magnetic scrutiny for the CS sample. The magnetic nanoparticles heating response to applied magnetic field and frequency is discerned at three distinct fields, where the outcome prevailed to inflated specific loss power for CS CZF in distinction to bare F and CZ samples for all the assessments. Remarkably; a lofty intrinsic loss parameter is also perceived for the CS sample recorded to about 5.36 nHm2 g−1; which is another eccentric outcome that significantly labels the CS CZF sample as a potentially high heating competence agent. This comprehension accords to a finer perspective to meliorate the theranostic environment for hyperthermia applications. [ABSTRACT FROM AUTHOR]

Strontium (Sr) substituted cobalt ferrite i.e. Co 1− x Sr x Fe 2 O 4 ( x =0.00, 0.01, 0.015, 0.02, 0.05, 0.1) have been synthesized by the citric acid modified sol–gel method. Crystal structure and phase purity have been studied by the X-ray powder diffraction technique. The Rietveld refinement of XRD pattern using the space group F d 3 ¯ m shows monotonically increasing of lattice parameter with the increase in Sr concentration. Magnetic hysteresis loops measurement has been carried out at room temperature using a vibrating sample magnetometer (VSM) over a field range of ±1.5 T. Magnetocrystalline anisotropy constant were calculated by employing the Law of Approach (LA) to the saturation. It is observed that magnetocrystalline anisotropy has anomaly for x =0.01 (Co 0.99 Sr 0.01 Fe 2 O 4 ) sample. Strain mediated modification of magnetic properties in Sr substituted cobalt ferrite has been observed. The saturation magnetization for doping concentration i.e. x =0.01 abruptly increase while for x >0.01 decreases with the increase in Sr concentration. A correlation between lattice strain and magnetic behavior in non-magnetic Sr- substituted nano-crystalline cobalt ferrite has been reported. [ABSTRACT FROM AUTHOR]

Strontium hexaferrite is a hard magnet that can help to develop rare-earth-free magnets for permanent magnet applications. A composition of SrFe 12-x-y Ni x Al y O 19 (0.005 ≤ x ≤ 0.02; 1 ≤ y ≤ 4) is successfully synthesized with by the sol-gel auto-combustion process, and the effect of Ni-Al substitution is studied on the structural, magnetic, dielectric, and electrical properties. The XRD analysis confirms the formation of magnetoplumbite hexagonal structure with P6 3 / mmc space group. Magnetic studies have shown a massive improvement in the coercivity (H c) of the samples. The highest ever H c value of 24.44 kOe in strontium hexaferrite-based rare-earth free magnet is attained for the SrFe 7.98 Ni 0.02 Al 4 O 19 ferrite composition. The energy density (BH) max is effectively tuned to 16.2 MGOe for the SrFe 8.985 Ni 0.015 Al 3 O 19 composition. The dielectric properties have shown the typical behavior of ferrites and are explained according to the Maxwell-Wagner and Koop model. The proposed work is expected to offer an immense possibility to improve the hard magnetic properties of strontium hexaferrite magnets comparable to the expensive NdFeB magnets in order to fully/partially replace them in different permanent magnet applications. [Display omitted] • An attempt to substitute Ni2+ & Al3+ ions at Fe3+ lattice site in SrFe 12 O 19 ferrite. • Highest ever H c value of 24.44 kOe is attained for SrFe 7.98 Ni 0.02 Al 4 O 19 composition. • Found an enhanced (BH) max value ∼16.2 MGOe for SrFe 8.985 Ni 0.015 Al 3 O 19 composition. • These ferrites offer the utmost probability to use in different PM applications. • This work suggests the exploration of SrM to improve its hard magnetic properties. [ABSTRACT FROM AUTHOR]

• Maximum (BH) max and reduced remanent are found to be 0.887 MGOe and 0.53, respectively, for (50)%BHF+(50)%CFO composite. • Exchange coupling is responsible for enhanced (BH) max and reduced remanent in the composite. • Henkel plot and derivative of magnetization vs field curve are used to explore the magnetic interaction between particles. The (x)% BaFe 12 O 19 (BHF) + (100-x)% CoFe 2 O 4 (CFO) (x = 0 to 100) magnetic composites are prepared to explore its magnetic properties. The XRD patterns reveal the presence of both BaFe 12 O 19 and CoFe 2 O 4 crystal symmetries in the composite. The FESEM and TEM micrographs reveal the uniform distribution of nanoparticles. The theoretical saturation magnetization is calculated by Vegard's law, which is nearly equal to the experimental observation. The maximum reduced remanent (M r /M s) and magnetic energy product (BH) max are found to be 0.43 and 0.456 MGOe, respectively, for x = 50 i.e. (50)% BHF + (50)% CFO. It is explained by assuming magnetic interaction at the interfaces of soft and hard magnetic phases. The coercive field, remannet magnetization, reduced remanent, saturation magnetization, and (BH) max increase with a decrease in measuring temperatures. The enhancement of magnetic parameters at a low temperature is observed due to the decrement of the thermal energy of magnetic moments at the surface. The saturation magnetization increases with an increase in annealing temperature, which could be due to the minimization of spin disorders at the surface of nanoparticles. The enhanced reduced remanent (M r /M s) and (BH) max are found for the (50)%BHF + (50)%CFO composite annealed at a higher temperature. The evidence of magnetic interaction between two magnetic phases in the composite has been realized by employing the Henkel plots and dM dH versus H curve techniques. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles of calcium (Ca)-substituted cobalt ferrite i.e. Co 1− x Ca x Fe 2 O 4 ( x =0.00, 0.01, 0.015, 0.02, 0.05, 0.1, and 0.15) have been synthesized by the citric acid modified sol–gel method. X-ray powder diffraction (XRD)patterns confirm the formation of spinel phase. The particle size decreases with the Ca concentration. The Rietveld refinement of XRD patterns using the space group – Fd 3 ̅ m shows monotonically increasing of lattice parameter with the increasing concentration of Ca. The FT-IR spectrum recorded in the range of 325–1000 cm −1 and Raman spectrum obtained in the range of 88–800 cm −1 shows the formation of spinel phase belonging to Fd 3 ̅ m space group supporting structural analysis from XRD patterns. Magnetocrystalline anisotropy has been obtained using “Law of Approach (LA) to Saturation magnetization”. Saturation magnetization and remnant magnetization is maximum for 1% Ca substitution which could be due to strain mediated magnetism. However these magnetic properties decrease with the Ca substitution for the percentage above 1%. It could be due to decrease of magnetic exchange interaction in the sample. A correlation between magnetic behavior and lattice strain has been established in non-magnetic Ca substituted nano-crystalline cobalt ferrite. In order to investigate the ferromagnetic nature of the sample, Arrott plot analysis has been carried out. Difference in saturation magnetization obtained from LA to saturation and Arrott plot analysis gives the qualitative information about the influence of lattice strain on saturation magnetization. [ABSTRACT FROM AUTHOR]

Beside the disappearance of characteristics superlattice reflections for R 3 c space group as (1 1 3) at 2θ =37.8°, the typical reflections of Pbnm space group as (1 1 1) at 2θ =25.42° as well as their new superlattice reflections such as (0 2 1), (0 2 3) and (2 2 1) at 2θ =34.14°, 47.69° and 47.82° which are characteristic of the antiparallel cation displacements has appeared for 7.5% of co-substitution (Eu in Bi site and Mn in Fe site) in BiFeO 3 . Morphological phase boundary has been observed around 7.5% of co-substitution which have enhanced remnant magnetization about 20 times that of pure one and it could be due to the suppression of cycloid spin structure and spin canting at the surface of nanocrystallites. Further increase in co-substitution percentage (>7.5%) leads to the reduction of remnant magnetization due to the appearance of collinear antiferromagnetic ordering in the Pbnm space group which becomes significant for higher co-substitution percentage. The analysis of diffuse reflectance spectra which shows the point group symmetry breaking from O h to C 3v supports the modification in local FeO 6 environment and structural transition. [ABSTRACT FROM AUTHOR]

Bi 1− x La x Fe 1− x Mn x O 3 ( x = 0.000–0.300) ceramics prepared by the tartaric acid modified sol–gel technique have been studied to analyze the effect of composition driven structural transition on the magnetic properties of bismuth ferrite (BiFeO 3 ). It was found that the co-substitution of La & Mn at Bi & Fe sites leads to suppression of impurity phases (Bi 2 Fe 4 O 9 and Bi 25 FeO 40 ) which generally appear in BiFeO 3 . The quantitative crystallographic phase analysis has been carried out by double phase Rietveld analysis of all the XRD patterns which indicates the existence of compositional driven crystal structure transformation from rhombohederal (space group R3c ) to the orthorhombic (space group Pbnm ) with the increase in substitution concentration. The 5% co-substituted sample exhibit high remnant magnetization i.e. about 15 times that of BiFeO 3 which is due to the suppression of cycloid spin structure and enhanced canting angle of antiferromagnetically ordered spins caused by the crystal lattice distortion. However, further increase in substitution results in the reduction of remnant magnetization and coercivity due to the appearance of complete antiferromagnetic ordering in the orthorhombic structure because of the significant contribution from the crystallographic phase of Pbnm space group (as obtained from double phase Rietveld analysis). The frequency independent higher dielectric constant and lower dielectric loss were observed for 5% co-substitution. Hence, this particular composition may be interesting for device applications. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of Bi1-xNdxFe1-xMnxO3 ceramics prepared by the tartaric acid modified sol-gel technique have been studied to understand the effect of structural modification on the magnetic Properties of BiFeO3. The co-substitution of Nd and Mn at Bi and Fe sites respectively in BiFeO3 significantly suppress the impurity phases (Bi25FeO40, Bi2Fe4O9 etc.). The Rietveld analysis of X-ray diffraction (XRD) patterns indicates the existence of compositional driven crystal structure transformation from rhombohederal (R3c space group, higher crystal symmetry) to the orthorhombic (Pbnm space group, lower crystal symmetry) with the increase in substitution concentration due to excess chemical pressure (lattice strain). The quantitative crystallographic phase analysis has been carried out by Rietveld analysis of all the XRD patterns. Magnetic measurements reveal that co-substituted BiFeO3 nanoparticles for x=0.050 have enhanced remnant magnetization about 21 times as compared to pure one. The remnant magnetization reaches a maximum value at the morphological phase boundary (x=0.050) and further increase (x>0.050) in substitution concentration results in the reduction of remnant magnetization due to the appearance of complete antiferromagnetic ordering in the orthorhombic structure because of the significant contribution from the crystallographic phase of Pbnm space group (as obtained from the quantitative crystallographic phase contribution by the Rietveld analysis). [ABSTRACT FROM AUTHOR]

• Gadolinium doping in BHF results in modification of magnetic properties. • "Law of Approach to Saturation" gives the magnetocrystalline anisotropy constant. • Para-ferrimagnetic transition is observed around 700 K. • Maximum entropy change and RCP are found to be 0.72 J/kgK and 27.5 J/kg, respectively, near Curie temperature. • Possibility to use the Gd doped BHF at high temperature as a cooling agent. Gd doped barium hexaferrite (BaFe 12−x Gd x O 19 , x = 0.0–0.7) has been synthesized by the sol-gel method to explore its magnetic and MCE (magnetocaloric effect) properties. The materials crystallize to hexagonal magnetoplumbite phase. Average particle size decreases with the increase in Gd concentration in barium hexaferrite (BHF). The coercive field increases from 3.2 to 4.8 kOe, and saturation magnetization decreases from 68.21 to 54.23 emu/g with the increase in Gd concentration from x = 0.0 to x = 0.7. These large changes in magnetic parameters reveal the effect of Gd concentration in BHF. The saturation magnetization monotonously reduces with an increase in Gd concentration in BHF due to a decrease in average particle sizes. The saturation magnetization is found to be higher at a lower temperature (60 K) compared to that of room temperature (300 K). It is due to a reduction in thermal energy at low temperature which is smaller compared to the magnetic Gibbs free energy at low temperature. Hence, the magnetic spins are freezing along the applied magnetic field direction at the low temperature. Also, the magnetocrystalline anisotropy constant (obtained by the "Law of Approach to Saturation method") is found to be more at low temperature compared to that of room temperature due to an increase in the strength of spin-orbit coupling with the decrease in temperature (i.e. thermal energy). The M-T curves and M-H hysteresis loops reveal paramagnetic to ferromagnetic transition at the Curie temperature. The maximum entropy change was found to be in the range of 0.12–0.72 J/kgK in a window of the applied magnetic field of 0.5–3 T, and the corresponding RCP max was found to be 2.5–27.5 J/kg. The present study opens a window to explore the MCE on BHF based material. [ABSTRACT FROM AUTHOR]

With an aim to explore the d0 ferromagnetism in Ag-doped ZnO compounds, the poly-crystalline samples of Zn 1 - x Ag x O (with 0 ≤ x ≤ 0.12) were synthesized by a standard solid-state synthesis technique. The XRD analyses indicated that these compounds have been formed as Ag:ZnO nanocomposite. According to scanning electron microstructural study, all compounds have a homogenous nearly spherical shape morphology. The EDS spectra reveal that the final produced compounds do not contain any unwanted external impurity. The magnetization versus field measurement at room temperature demonstrates that the undoped ZnO compound shows ferromagnetism embedded in diamagnetic matrix, whereas all Ag-doped ZnO samples exhibit a clear room temperature ferromagnetic behavior with coercivity values between 80 and 196 Oe. The maximum saturation magnetization was obtained for the Zn0.97Ag0.03O sample; however, it declines subsequently. The bound magnetic polarons (BMPs) has been considered to explain the observed ferromagnetic behavior. [ABSTRACT FROM AUTHOR]

Ho3+ion-substituted nanocrystalline cobalt ferrite materials with the chemical formula CoFe2−xHoxO4forx = 0.0, 0.025, 0.05, 0.075 and 0.1 have been synthesised by standard citrate precursor method. Crystal structure and phase purity have been studied by powder X-ray diffraction (XRD) method by employing Rietveld refinement technique. The distribution of cations between the tetrahedral site (A-site) and octahedral site (B-site) has been estimated by Rietveld analysis. The refinement result shows that Ho3+ion has a strong preference for octahedral sites (B-sites). The lattice constants decrease with the Ho3+concentration up tox = 0.05. Crystallite size decreases with the Ho3+concentration. The magnetic hysteresis loop measurements have been carried out at room temperature using a vibrating sample magnetometer (VSM) over a field range of ±2 T. The magnetisations in saturation have been analysed by employing the ‘law of approach (LA)’ technique. The magnetocrystalline anisotropy constant and saturation magnetisation are found to decrease with the Ho3+concentration up tox = 0.05. The coercivity decreases with the Ho3+concentration. The vibrational modes of the octahedral and tetrahedral metal complex in the sample have been carried out using Fourier transform infrared spectroscopy (FT-IR). The FT-IR spectra of the samples have been analysed in the wave number range of 350–1000 cm−1. We have observed two prominent absorption bands which are assigned to tetrahedral and octahedral metal complexes. The elemental analysis has been carried out using energy dispersive spectroscopy (EDS) with the help of field emission scanning electron microscope (FE-SEM) and the results reveal that, elements are as per the stoichiometric ratio in all the samples. [ABSTRACT FROM AUTHOR]

Highlights: [•] Secondary phase formation has been controlled for Bi0.9Ca0.1Fe0.9Ti0.1O3 [•] Co-substitution of Ca & Ti at Bi & Fe sites significantly increases MS and HC [•] Compositional driven structural transition from rhombohedral to orthorhombic symmetry. [•] The leakage current has reduced significantly for Ca2+ and Ti4+ co-substituted BiFeO3. [•] Small band gap of co-substituted BiFeO3 may be useful for optoelectronic devices. [Copyright &y& Elsevier]

Pure 2 based wide band gap semiconductors were prepared by mechanical alloying method by using steel and tungsten carbide vials. They were further annealed at 900°C. The XRD patterns could be refined by using P42/ space group with typical lattice parameters a = b = 4.7322 Å and c = 3.1848 Å. The as milled powders obtained from both the vials exhibit room temperature ferromagnetism (FM) without any transition element doping. However upon annealing, the FM was destroyed in one of the samples. The observed FM is explained in terms of oxygen vacancy and defects induced electrons and exchange interaction between them. The ferromagnetic transition temperature obtained from the temperature variation of magnetization was found to be 915 K. The initial magnetization data could be analyzed in terms of bound magnetic polaron model. The resonance field shift in electron spin resonance spectrum is explained in terms of observed ferromagnetism. [ABSTRACT FROM AUTHOR]

Abstract: CoFe2−x La x O4 (x =0.0, 0.025, 0.05, 0.075 and 0.1) samples with different crystallite sizes have been synthesized by the citrate precursor method. All the XRD patterns could be analyzed by the Rietveld refinement technique using the space group. The cations distribution between the tetrahedral (A-site) and octahedral sites (B-site) has been estimated by Rietveld analysis. The refinement results show that La3+ ions have strong preference for octahedral sites (B-sites). The presence of Co, Fe, La and O ions in the sample has been obtained by energy dispersive spectroscopy (EDS) with the help of Field Emission Scanning Electron Microscopy (FE-SEM). The saturation magnetization has been analyzed by the “Law of Approach (LA)” technique. The saturation magnetization, magnetic coercivity and magnetocrystalline anisotropy constants are found to decrease with the increase of La3+ concentration. The saturation magnetization, coercivity and magnetocrystalline anisotropy constants increase with the increase of crystallite size. [Copyright &y& Elsevier]

Nanocrystalline cobalt ferrite (\CoFe2{\O}4) materials have been synthesized by citrate precursor and co-precipitation method. Samples are annealed at different temperatures to obtain the different nanocrystallite-size materials. All the samples crystallize to Fd\overline3m space group in cubic symmetry. Magnetic hysteresis loops measurement has been carried out at room temperature using a vibrating sample magnetometer (VSM). The magnetic data in the saturation region have been analyzed by employing the law of approach (LA) to saturation technique. The anisotropy constant ( K1) is found to be higher in citrate precursor derived samples. The saturation magnetization ( Ms), coercivity ( Hc), remanent magnetization ( Mr) and anisotropy constant ( K1) increases with the increase of crystallite size. [ABSTRACT FROM AUTHOR]

Abstract: Aluminium substituted cobalt ferrite nanocrystalline materials with chemical formula CoFe2−x Al x O4 (x=0.0−0.4) have been synthesised by citrate precursor method. The crystal structure and phase purity were studied by powder X-ray diffraction (XRD). All the XRD patterns have been analysed by Rietveld refinement technique using the space group. The unit cell volume, average crystallite size, effective bond lengths and lattice parameters decrease with Al3+ concentration. Magnetic hysteresis loop measurements were carried out at room temperature using a vibrating sample magnetometer over a field range of ±2T. The saturation magnetisation, coercivity and Remanent magnetisation decrease with Al3+ concentration. The magnetic data in saturation have been analysed by employing the law of approach technique. The anisotropy constants are found to decrease with Al concentration. The saturation magnetisation, coercivity, remanent magnetisation and anisotropy constant increase with crystallite size. [Copyright &y& Elsevier]

Introduction: Having long experience of open upper abdominal surgery under spinal anesthesia and laparoscopic cholecystectomy under general anesthesia, we performed this study of laparoscopic cholecystectomy with low-pressure pneumoperitoneum under spinal anesthesia to assess its safety and feasibility. Materials and Methods: In a private rural health set-up, 300 patients were selected prospectively for laparoscopic cholecystectomy under low-pressure (8 mm) pneumoperitoneum under spinal anesthesia in a span of three years. Only 3.5 ml of 0.5% bupivacaine was used for spinal anesthesia. Fourth port positioned at lower than usual at the level of umbilicus, change of position of the table with different stages of operation, massaging of right shoulder in cases of shoulder pain, removal of smoke if formed during dissection to diminish shoulder pain and holding the body of the gallbladder by the fourth port grasper at the level of lower margin of the liver in cases of long gallbladder were some modifications of standard laparoscopic cholecystectomy made in this study. Results: We successfully performed the operations in 291 patients without major complications. Four patients denied operation under spinal anesthesia. Spinal anesthesia was converted to general anesthesia in two patients due to severe shoulder pain. The operation was converted to open cholecystectomy in three patients. Mean age was 34.6 years (range 21-82 years). Mean BMI was -23.1 (range 20.8-28.3). Mean duration of operation was 39.6 min (range 18-78 min). Mean O2 saturation was 97.6%. Mean peak respiratory rate was 23.4 (range 16-38). 90.08% patients complained of right shoulder pain - most of them managed by shoulder massage alone. All patients were satisfied on follow up. Conclusion: Laparoscopic cholecystectomy under spinal anesthesia with low-pressure pneumoperitoneum can be performed safely and satisfactorily without major complications by experienced surgeons. [ABSTRACT FROM AUTHOR]

Nanocrystalline TiO2 sample was prepared by high-energy ball mill method. A known quantity of anatase phase-TiO2 was milled for 83 h in air. The samples were collected at intervals of 5 h of milling. The XRD patterns were recorded for all the samples. The crystal structure changed from anatase phase for bulk material to rutile-rich phase for nanocrystalline material. Nanocrystalline TiO2, which is a mixture of anatase, rutile, and srilankite phase, was prepared by milling for 60 h. The XRD pattern of unmilled anatase phase of TiO2 could be refined with I41/amd space group. The crystallite size of the TiO2 was found to decrease with milling time upto 50 h and then the size of rutile phase increases while the sizes of anatase and srilankite phases remain constant upto 60 h of milling. After 60 h, the sizes of all the phases remain constant. The average crystallite size for rutile phase is found to be 12 nm after 60 h of milling. [ABSTRACT FROM AUTHOR]

A 29-year female presented with recurrent biliary colic within few days of laparoscopic cholecystectomy for cholecystolihiasis. Magnetic resonance cholangiography demonstrated the presence of remnant gallbladder with the stone. Laparoscopic surgery was performed for removal of remnant gallbladder and stone with success. Early recurrence of biliary pain heightened suspicion of retained gallstone disease and need evaluation of biliary tract. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful synthesis of PVP capped doped CuS quantum dots. • A marked increase in the band gap of the quantum dots. • Low field magnetic interactions at room temperature. Polyvinlypyrrolidone (PVP) capped and magnetic transition metals (TM = Fe, Co and Cr) doped CuS quantum dots (Cu 1- x TM x S; x = 0.02 & 0.04) were synthesized by low entropy facile chemical co-precipitation method. The structural, optical and magnetic characterizations of the synthesized QDs were done by using X-ray diffraction (XRD) technique, UV–Vis-NIR absorption spectroscopy, photoluminescence (PL) spectroscopy and superconducting quantum interference device (SQUID) respectively. The low field non-linearity and the presence of coercivity in the M−H loops indicate the presence low field magnetic (spin–spin) interactions between the doped cations. [ABSTRACT FROM AUTHOR]

Abstract: Cerium-doped Y1− x Ce x MnO3 compounds have been prepared in single-phase form for x=0 to 0.10. X-ray diffraction (XRD) patterns could be analyzed by using P63cm space group. Temperature variations of ac susceptibility and magnetization measurements show that these Ce-doped materials exhibit weak ferromagnetic transition. The observed ferromagnetic transition is attributed to the double exchange ferromagnetic interaction between Mn2+ and Mn3+ ions due to electron doping. The M–H loops exhibit hysteresis along with linear contribution and were analyzed based on bound magnetic polaron (BMP) model. Increase in saturation magnetization and decrease in BMP concentrations have been observed with increase in Ce doping. [Copyright &y& Elsevier]

Abstract: Herein we report the generation of Au nanoparticles (NPs) by sparingly soluble acetanilide in water. We also report the formation of linear chain-like superstructures of self-assembled Au NPs, in the presence of excess acetanilide. This was achieved in two different ways. In the first method, acetanilide was added, with increasing concentration, into aqueous HAuCl4 to produce Au NPs as well as for the formation of assembly, which varied according to the concentration of acetanilide. The other route involved formation of spherical Au NPs at the lowest concentration of acetanilide, which was followed by the formation of assembly of various lengths upon further addition of variable amount of acetanilide. The assemblies were stable in aqueous solution for days with characteristic UV–vis absorption spectra consisting of two peaks. While the wavelength of the first peak remained the same, the position of the second peak changed to longer wavelength with increasing acetanilide concentration. Interestingly, the linear chain-like arrays could be broken into individual particles by first dilution of the solution concentration followed by treatment with ultrasonic waves. The individual Au NPs again formed linear chain-like arrays upon addition of excess acetanilide. [Copyright &y& Elsevier]

Abstract: La0.85Ag0.15Mn1− y Al y O3 compounds were prepared for y =0 to 0.20 by solid-state route. X-ray diffraction (XRD) patterns were recorded at room temperature and could be refined by using space group by employing Rietveld techniques. Temperature variations of ac susceptibility down to 30K were measured at an ac field amplitude of 6Oe. All the samples exhibit paramagnetic to ferromagnetic transition and the transition temperature decreases at the rate of 1.6K/Al%. Temperature variations of dc electrical resistivity and magneto-resistivity at 10kOe were measured down to 25K for all the above samples. Metal–insulator (M–I) transition has been observed for all the samples with transition temperature (T p) ranging from 285 to 213K. Resistivity in the metallic region could be explained on the basis of combination of electron–electron and electron–magnon scattering. [Copyright &y& Elsevier]

Abstract: The linear and nonlinear AC susceptibility as a function of temperature were measured on LaMn1− x Cu x O3 compounds for . Samples with exhibit paramagnetic to ferromagnetic transitions followed by low temperature spin glass like transition. The linear susceptibility exhibits strong frequency dependence and is analyzed in terms of standard theoretical model for spin glass. The magnitude and peak temperature of nonlinear susceptibility vary with AC field amplitudes. They are analyzed in terms of critical behaviour in the vicinity of spin glass transition temperature and the critical exponent is found to be 3.2. [Copyright &y& Elsevier]

Electron-doped Sr1-xLaxMnO3(0≤x≤0.50) and hole-doped (x=0.70 and 0.82) samples have been prepared by solid state route. X-ray diffraction patterns could be refined using P63 space group for x≤0.30 and $R\bar 3c$ space group for x≥0.40. Temperature variation of AC susceptibility measurements show that all the electron-doped materials exhibit paramagnetic to ferromagnetic transitions with the transition temperatures ranging from 375 to 393 K, followed by low temperature antiferromagnetic transitions. The ferromagnetic maximum susceptibility is found to increase systematically with La doping, i.e. with increase in Mn3+ ions. The high temperature resistivity data could be analyzed using the Mott-variable range hopping model. The hole-doped materials exhibit ferromagnetic to paramagnetic transition. [ABSTRACT FROM AUTHOR]

Abstract: Copper doped, CaMn1−x Cu x O3 compounds have been prepared in single phase form for x =0–0.20. XRD patterns could be analyzed using Pbnm space group with typical lattice parameters a =5.276Å, b =5.259Å and c =7.459Å. All samples exhibit antiferromagnetic transitions with Neel temperatures around 124K. The temperature variations of electrical resistivity follow the semi-conducting behaviour and they could be analyzed using variable range hopping with Coulomb interaction (ES-VRH) model. The Cu doping is found to enhance the antiferromagnetic interactions. [Copyright &y& Elsevier]

Abstract: Ba1−x La x MnO3 compounds for x =0.30–0.70 have been prepared in single phase form. Structural transition from orthorhombic symmetry to rhombohedral symmetry has been observed with increase in doping. ac Susceptibility measurements show that all the above materials exhibit paramagnetic to ferromagnetic transitions. Metal–insulator transitions have been observed in electron doped as well as hole doped materials, and the transition temperatures vary from 243 to 340K. Reentrant semiconducting behaviour is observed in the vicinity of charge ordering temperature in x =0.50 sample. The colossal magneto-resistivity values are mostly found to increase with decrease in temperature. The correlation between ac susceptibility and electrical resistivity results has been discussed. The low temperature metallic behaviour could be explained only by the electron–electron scattering mechanism in both electron and hole doped materials. [Copyright &y& Elsevier]

LaMn1-xCuxO3 compounds have been prepared in single phase form for x - 0 to 0.30. X-ray diffraction patterns recorded at room temperature could be mostly refined using Pbnm space group. Paramagnetic-to-ferromagnetic transitions have been observed up to x = 0.30, from ac susceptibility measurements. Metal-insulator transition in the vicinity of ferromagnetic transition temperature has been observed for x = 0.05 and the resistivity data in the metallic region could be explained in terms of electron-electron and electron-magnon scattering mechanisms. Further increase in Cu-doping beyond x = 0.05 leads to systematic decrease in ferromagnetic transition temperature and ultimately ferromagnetism is destroyed for x = 0.40. The resistivity data of all samples except x = 0.05 exhibit semiconducting behaviors and they could be mostly explained using the adiabatic small polaron hopping model. [ABSTRACT FROM AUTHOR]

La1-xAgxMnO3 compounds have been prepared for x=0–0.35. The X-ray diffraction patterns for x=0 and 0.05 could be refined by using Pbnm space group, whereas for x≥0.10, they could be refined by using R&3macr;c space group. Measurements of ac susceptibility show that all the above Ag-doped samples exhibit paramagnetic to ferromagnetic transitions in the temperature range 251–294 K. The freezing of spin glass like behavior has been observed at around 100 K. The above Ag-doped samples exhibit metal–insulator transitions in the temperature range (TMI) 242–290 K. The resistivity data in the metallic region could be fitted to the expression corresponding to electron–electron scattering mechanism. [Copyright &y& Elsevier]

Temperature variation of DC electrical resistivity and magneto-resistivity have been measured on mono-valent, Ag- doped La1−xAgxMnO3 compounds for x=0.05–0.30. All these samples exhibit metal–insulator transitions and the transition temperature increases with applied field. The resistivity data in the metallic region, i.e. below the transition temperature could be fitted to the empirical relation ρ=ρ0+ρ1Tn. The value of exponent n, mostly varies from n=3 for zero field case to n=2 for 50 kOe field. The electrical transport in zero field is controlled by strong spin fluctuations scattering and in the presence of high magnetic field, it is mostly due to electron–electron scattering. The applied magnetic fields are found to suppress the scattering due to spin fluctuations. The resistivity data in the semiconducting region, i.e. above the transition temperature could be fitted to Mott variable range hopping model. The applied magnetic fields tend to delocalize the charge carriers in the semiconducting region and thereby decrease in hopping energy and increase in density of states has been observed. Colossal magneto-resistivity have been observed in all the above samples and the maximum value is found to be 73% for x=0.15 sample for 50 kOe field. [Copyright &y& Elsevier]

La1−xCuxMnO3 compounds have been prepared in single phase form for x=0–0.20. X-ray diffraction (XRD) patterns were recorded at room temperature and these could be refined using R3¯c space group by employing rietveld method. The typical lattice parameters for x=0.10 sample are a=b=5.531 A˚ and c=13.352 A˚. dc electrical resistivity measurements were carried out below room temperature. The samples x≤0.10 exhibit metal–insulator transitions in the temperature range (TMI) 43–92 K. The resistivity data above TMI could be fitted to Mott variable range hopping (Mott-VRH) model. The samples x>0.10 could be mostly fitted to Efros–Shklovskii VRH (ES-VRH) model. Temperature variations of ac susceptibility down to 30 K were measured at an ac field amplitude of 5.3 Oe. All the above Cu doped samples exhibit paramagnetic to ferromagnetic transitions. [Copyright &y& Elsevier]

X-ray diffraction, electrical resistivity and ac susceptibility measurements have been carried out on La1—xAgxMnO3 compounds for x = 0.05 to 0.30. These samples are found to be in single phase form with R&3oline;c space group and with typical lattice parameters a = b = 5.524 Å and c = 13.349 Å for x = 0.05 sample. The Mn­O­Mn bond angles and variance, σ2 are found to increase with doping. Metal-insulator transitions in the temperature range 254 to 259 K have been observed. These materials exhibit paramagnetic to ferromagnetic transitions in the vicinity of metal-insulator transition temperatures. The paramagnetic susceptibility could be analyzed using Curie­Weiss law. All the above samples exhibit colossal magneto-resistivity and its maximum value is found to be 73% for x = 0.15 sample at 50 kOe magnetic field. [ABSTRACT FROM AUTHOR]

We report ferromagnetic behavior in undoped ZnO nanofibers prepared by electrospinning a solution of zinc acetate and poly vinyl alcohol followed by annealing at 550°C for about 90min. X-ray diffraction patterns of the heat treated as-spun composite fibers reveal the formation of ZnO nanowires in wurtzite structure with no noticeable impurity phases. ZnO nanowires annealed between 500°C and 600°C exhibited room temperature ferromagnetism with decreasing magnetization with increasing annealing temperature. Room temperature ferromagnetism was observed in as-spun fibers annealed in air as well as under vacuum. However, vacuum annealed nanofibers show higher magnetization as compared to air annealed fibers, which indicates that oxygen vacancy is a cause for the observed room temperature ferromagnetism in the ZnO nanofibers. [ABSTRACT FROM AUTHOR]

The (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 (0-3 type particulate) nanocomposites with x = 0.00, 0.02, 0.04, 0.06, 0.08, and 1.00 were prepared by the solid-state method. Cobalt ferrite crystallized into cubic crystal symmetry with an F d 3 ̄ m space group. Strontium-substituted barium titanate crystallized into a tetragonal crystal structure with a P4mm space group. Field emission scanning electron microscopy and transmission electron microscopy techniques show the distribution of different sizes of particle. Polarization vs electric field curves show the highest maximum polarization (Pm) of 10.26 μC/cm2, remnant magnetization (Pr) of 11.70 μC/cm2, and coercivity (Ec) of 19.95 kV/cm for x = 0.04 composition at 35 kV/cm. However, it is smaller than the Ba0.8Sr0.2TiO3 phase (Pm = 16.86 μC/cm2, Pr = 13.20 μC/cm2, and EC = 10.80 kV/cm). The highest dielectric constant of around 9800 was found for x = 0.04 composition, with a very small dielectric loss factor of about 0.02, i.e., less than even 2%. This is ∼10 times compared to that of Ba0.8Sr0.2TiO3 (BSTO), which has been explained by considering interaction at the interface of CoFe2O4 (CFO) and BSTO, leakage current, and variation of the lattice parameter of BSTO in (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 nanocomposite. The magnetic hysteresis loops show squeezing near the origin. The magnetic parameters like coercivity, remnant magnetization, and saturation magnetization increased with the increase in the CoFe2O4 weight fraction. Magnetic interaction between surfaces of magnetic CFO and non-magnetic BSTO is evident from the ΔH vs M plots, and it also evidences the magnetism at the surface of BSTO due to uncompensated spins. [ABSTRACT FROM AUTHOR]

The activities of several enzymes related to amino acid metabolism were investigated in senescing detached wheat leaves (Triticum aestivum L. cv. Diplomat) in light and darkness and after kinetin treatment. Glutamine synthetase and glutamate synthase activities rapidly declined in darkness. In light, the decline of glutamate synthase activity was retarded, while the activity of glutamine synthetase remained high and even increased transitorily. Kinetin treatment counteracted the decline of the activities of both enzymes. The activity of glutamate dehydrogenase markedly increased during senescence, particularly in light, and kinetin treatment lowered its activity. The activities of glutamate-oxaloacetate and glutamate-pyruvate amino- transferases and of NADP-dependent isocitrate dehydrogenase also increased in detached wheat leaves in light. Kinetin treatment prevented the rise of these enzyme activities. In darkness, the activities of glutamate-oxaloacetate aminotransferase and NADP-dependent isocitrate dehydrogenase decreased slowly while the decline of glutamate-pyruvate aminotransferase activity was more rapid. The activity of NAD-dependent malate dehydrogenase decreased both in light and, more rapidly, in darkness. The pattern of changes of the enzyme activities provides an explanation for the amino acid transformations and the flow of amino nitrogen into transport metabolites in senescing leaves. [ABSTRACT FROM AUTHOR]

Barium hexaferrite is known to be a very good ferromagnetic material. However, it shows very good dielectric properties, i.e., the dielectric constant is comparable to that of the ferroelectric material. However, its crystal symmetry does not allow it to be a ferroelectric material. Hence, the electrical properties have revived the considerable research interest on these materials, not only for academic interest, but also for technological applications. There are a few reports on temperature dependent dielectric behavior of these materials. However, the exact cause of dielectric as well as electrical conductivity is yet to be established. Hence, Al (very good conducting material) substituted barium hexaferrite (BaFe12-xAlxO19, x=0.0-4.0) has been prepared by following the modified sol-gel method to understand the ac and DC electrical properties of these materials. The crystal structure and parameters have been studied by employing the XRD and FTIR techniques. There are two transition temperatures, which have been observed in the temperature dependent ac dielectric and DC resistivity measurement. The response of dielectric behaviors to temperature is similar to that of the ferroelectric material; however, the dielectric polarization is due to the polaron hopping, which is evident from the DC resistivity analysis. Hence, the present observations lead to understand the electrical properties of barium hexaferrite. The frequency dependent dielectric dispersion can be understood by the modified Debye model. More interestingly, the dielectric constant decreases and DC resistivity increases with the increase in the Al concentration, which has the correlation between bond length modifications in the crystal due to substitution. [ABSTRACT FROM AUTHOR]

Introduction: The Lichtenstein technique is currently one of the popular methods in practice as it provides very good results consistently. However many patients suffer from wound indurations' and chronic wound pain which are often underreported. The transinguinal preperitoneal technique (TPT) avoids these complications by placing the mesh in preperitoneal plane by open approach. Materials and Methods: In this study, 71 patients were randomized into two groups one, of which one underwent the Lichtenstein repair and the other preperitoneal repair by TPT. All the patients were followed up for two years. Results: Patients in TPT group had less pain in immediate postoperative period (p - .005), less wound induration and chronic pain on follow-up. Patients were also able to return to work early (p =0.036). Average duration of operation was slightly longer compared to Lichtenstein technique (p < .0061). There was no recurrence in either group on 2 year follow-up. Conclusion: This study shows that TPT provides a better alternative to Lichtenstein technique with decreased incidence of wound complications and chronic groin pain, while having a similar recurrence rate. Preperitoneal mesh placement by open approach in TPT is also easier and eliminates the need for laparoscopy. [ABSTRACT FROM AUTHOR]

Lead-free ferroelectric materials are essential for environment-friendly solid-state cooling technology. In this respect, the electrocaloric effect of lead-free Ba0.8−xSr0.2SmxTiO3 (x = 0.01–0.05) ceramics has been investigated. The Rietveld refinement reveals that all the ceramics exhibit tetragonal symmetry and the tetragonality decreases for x > 0.03, which is the major reason behind the decrease in both isothermal entropy change and adiabatic temperature change. The degree of diffuseness parameter is enhanced by doping of Sm3+, which confirms the formation of polar nanoregion and the enhancement of the electrocaloric effect parameter by adding extra entropy. The relaxor behavior of the prepared samples is also confirmed by estimating the degree of deviation parameter (Δ T m = 77 K ) from the 1 ε r vs. T curve. So, the temperature stability of the prepared ceramics is improved in a broad temperature window. The highest isothermal entropy change (Δ S) , adiabatic temperature change (Δ T) , and electrocaloric strength ( Δ T Δ E ) are found to be 1.230 Jkg−1 K−1, 0.862 K, and 0.028 73 K cm/kV at 316 K, respectively, for Ba0.77Sr0.2Sm0.03TiO3. [ABSTRACT FROM AUTHOR]

The crystal structure of La 0.7 Sr 0.3 Mn 1−x Al x O 3 (LSMAO) with x = 0,0.025,0.05,0.075 and 0.10 ceramics prepared by the Sol-gel method were investigated by employing the XRD technique. The XRD patterns analysis by employing the Rietveld analysis confirms the nonexistence of secondary crystal phase/s and, materials are crystallized to the R-3c(167) space group. The microstructural properties were studied using scanning electron microscope (SEM) and transmission electron microscope (TEM). The dielectric property, AC conductivity, complex impedance spectroscopy and complex electrical modulus have been studied over a wide range of frequencies (103 Hz–107 Hz) at different temperatures from 313K to 393K. The Non-Debye type relaxation process has been observed in synthesized samples confirmed from the Nyquist plot. The Cole-Cole plots were employed to estimate the individual grain and grain boundary contributions. The Maxwell-Wagner (MW) polarization model provides an explanation for the greater values of dielectric constant at the lower frequencies. The present study explores the technological usefulness of LSMAO. [ABSTRACT FROM AUTHOR]

The larval form of the parasite Echinococcus granulosus causes a hydatid cyst. The most common sites are liver and lungs. We present an unusual case of an isolated primary hydatid cyst of the spleen. In our case, ultrasonography images of the spleen were not suggestive of hydatid disease except a large cystic lesion. We proceeded to conservative splenectomy that detected hydatid cyst incidentally during operation. This issue is considered common in our geographical area. A high suspicion of this disease is justified in endemic regions. Moreover, medical treatment should precede and follow the surgical intervention. [ABSTRACT FROM AUTHOR]

Abstract: The phosphate uptake potential was significantly stimulated with low concentration of salicylic acid (SA). In one of the wheat cultivars (Triticum aestivum Var. Sonalika), 50μM SA stimulated phosphate (PO4 3−) uptake. At higher concentrations of SA (500 and 1000μM), the rate of uptake was reduced. These findings underscore the light and dose-dependent biphasic action of SA: a low 50μM stimulated, and high concentrations 500 and 1000μM inhibited, PO4 3− uptake. [Copyright &y& Elsevier]

The CoFe2-xMnxO4 compound is prepared by following the sol gel technique. The structural analysis through XRD and Rietveld has been confirmed for the single cubic phase having ... space group for CoFe2-xMnxO4 and also verified it through Raman spectroscopy measurements. The tetrahedral site observed to be red shifted with increase in Mn concentration in cobalt ferrite. All the XRD patterns have been analyzed by employing the Rietveld refinement technique. The particle size was found to be in the range of 30-40 nm. The electrical properties of polycrystalline CoFe2-xMnxO4 for x=0.00, 0.10, 0.15, and 0.2, spinel ferrite was investigated by impedance spectroscopy. The influence of doping, frequency and temperature on the electrical transport properties of the CoFe2-xMnxO4 for x=0.00, 0.10, 0.15, and 0.20 were investigated. The magnitude of Z' and Z" decreases with increase in temperature. Only one semicircle is observed in each Cole Cole plot which reveals that ac conductivity is dominated by grains. The grain resistance and grain boundary resistance both were found to decrease as a function of temperature. Temperature variation of DC electrical conductivity follows the Arrhenius relationship. A detailed analysis of electrical parameters provides assistance in connecting information regarding the conduction mechanism as well as determination of both dielectric and magnetic transition temperatures in the substituted cobalt ferrite. Detailed analysis of ac impedance and DC resistivity measurement reveals that, the magnetic ordering temperature in the Mn substituted cobalt ferrite does not respond to the frequency of ac electrical signal; however, it responds to the DC resistivity. The correlation between ac impedance and DC resistivity has been established. [ABSTRACT FROM AUTHOR]

Polycrystalline [(0.5) Bi0.5Na0.5TiO3-(0.5) LaFeO3] multiferroic composite is prepared by using the solid-state reaction method. The crystal structure of both phases is characterized by using the X-ray diffraction method (XRD) and confirms the presence of rhombohedral (i.e., bismuth sodium titanate) and orthorhombic (i.e., lanthanum ferrite) phases in the composite. The microstructure of the composite is analyzed using field emission scanning electron microscopy (FESEM). The crystal structure is further studied with Raman spectroscopy. The present composite exhibits ferroelectric and ferrimagnetic-like properties, revealing its multiferroic behavior. Furthermore, the impedance analysis of the composite shows the negative temperature coefficient of resistance behavior. The present study describes the structural and physical properties of the possible lead-free multiferroic composite. [ABSTRACT FROM AUTHOR]

• Sr doped LCMO double perovskite nanoparticles were synthesized using sol–gel method. • Nanoparticles were studied using XRD, TEM, FTIR, Raman, Uv–Vis and M−H curves. • Resistivity curve (R-T) suggest the semiconducting nature for the compound. • M−H and ZFC-FC curves show the interesting magnetic properties of Sr doped LCMO. A study on crystal structure and physical properties has been performed on nanoparticles of lead-free double perovskites, La 2 CoMnO 6 (LCMO) and Sr-doped La 2-x Sr x CoMnO 6 (LSMO:0 ≤ x ≤ 0.08) prepared by the sol–gel synthesis method. In preparation for the LSMO nanoparticle, the La site of the LCMO double perovskite was replaced with an increasing concentration of Sr atom. Structural investigation done by employing the X-ray Diffraction technique indicates that the crystallite size decreases as the doping concentration increases. The Rietveld refinement on the XRD pattern shows the formation of the rhombohedral phase of LCMO (S.G. no. 161). Strain in the prepared samples estimated from Williamson Hall (W-H) analysis shows that the strain decreases as crystallite size decreases. The presence of compressive strain is also evident from the blue shift obtained in the Raman spectrum of the nanoparticles. The UV–Vis spectra reveal the maximum absorption in the near UV region of the electromagnetic spectrum. The Bandgap analysis from Tauc's plot shows an increase in band gap with Sr doping in the LCMO host lattice (from 1.81 eV to 1.92 eV). This is attributed to the decrease in crystallite size and octahedral tilting with Sr doping. Resistivity versus temperature plots reveal the semiconducting nature of the compound. A linear nature graph between l n ρ and T - 1 4 indicates that the electric transport mechanism is governed by the variable range Hopping (VRH) model. The M−H curves show that the maximum magnetization decreases as a result of Sr doping due to the anti-site disorder introduced. dM/dT vs T curve shows two magnetic transitions at ∼ 215 K and at ∼ 173 K which are due to Co2+–O2--Mn4+ and Co3+–O2--Mn4+ ferromagnetic superexchange interactions, respectively. [ABSTRACT FROM AUTHOR]