Citrate Gel Research Articles

Structural, electrical, leakage current, and magnetic characteristics of double perovskite Nd2NiTiO6

AbstractThis study investigates the structural, electrical, leakage current, and magnetic characteristics of the double perovskite material Nd2NiTiO6 synthesized through the sol–gel citrate auto‐ignition method. The Rietveld refinement of the X‐ray diffraction patterns confirmed a monoclinic symmetry (space group P21/n) with an ordered arrangement of alternate NiO6 and TiO6 octahedra. Impedance spectroscopic analysis exhibited the material's non–Debye‐type relaxation mechanism and semi‐conductive nature. AC conduction analysis revealed that the conduction of charge carriers occurs via the nonoverlapping small polaron hopping mechanism, consistent with Mott's variable range hopping model. Temperature‐ and frequency‐dependent dielectric measurements were interpreted using the Maxwell–Wagner interfacial polarization model. The analysis of thermal‐ and field‐dependent leakage currents established that conduction is ohmic, which the Schottky barrier model explains. Studies on magnetization ruled out the presence of magnetic ordering connected to indirect interaction between Ni2+ ions via Ti4+ ions and the rare‐earth cation (Nd3+) moment.

Structural, Morphological, Optical and Dielectric Studies of RE3+ Doped CoFe2O4

Cobalt ferrite nanoparticles, both undoped and Eu³⁺-doped, with the formula CoEuxFe2-xO4 (where x = 0.00 and 0.10), were produced using the citrate gel auto-combustion technique. X-ray diffraction confirmed the successful formation of the phase and the purity of the synthesized nanoparticles. The morphological analysis was conducted using scanning electron microscopy (SEM). The optical properties of cobalt ferrite were analyzed using UV-Vis spectrometer. Dielectric properties, such as the real part of the dielectric constant and loss tangent, were evaluated using an LCR meter. Doping cobalt ferrite nanoparticles with europium resulted in a significant improvement in charge storage and transport characteristics.

The effects of processing technique on formation temperature of calcium aluminate magnesium (CaO.2MgO.8Al2O3)

This study aims at the synthesis of a ternary phase crystal CaO.2MgO.8Al2O3 (CM2A8) in the Al-rich part of the ternary system CaO-Al2O3-MgO through two techniques: (1) sol–gel citrate and (2) solid-state reaction. Based on the measurement of particle size, density, phase analysis, nature of bounds, and microscopic observation, the effect of the processing technique on the crystal purity, crystallite size, and synthesis temperature of the as-prepared CM2A8 powder was investigated. Phases analysis (XRD patterns) showed in the sol–gel citrate combustion method almost a single-phase material (calcium aluminate magnesium phases) at relatively lower temperatures while in the solid-state method as-prepared CM2A8 powder with a small amount of spinel (MgAl2O4 = MA) and calcium hexaaluminate (CaAl12O19 = CA6) secondary phases. The generated heat through the combustion of the reaction of ammonium nitrate and citrate-based complexes decreases the synthesis temperature of nanocrystalline CM2A8, and the CM2A8 phase is formed at a temperature of 1400 °C. While growth mechanism in the solid-state reaction method adheres to the two-dimensional nucleation theory and a thick hexagonal flake known as CM2A8 is produced at a temperature of 1700 °C. In comparison with the crystals synthesized by the solid-state reaction method, the powder density of the nanocrystals synthesized by a sol–gel combustion method exhibits higher values (3.54 g.cm−3 and 3.65 g.cm−3, respectively). Peak intensities in the 400–1000 cm−1 range, according to FTIR measurements, correspond to metal–oxygen–metal (M–O–M) bonds (vibrations of Al–O stretching in Mg–O–Al and Ca–O–Al), and they grow as the temperature rises from 200 °C to 1400 °C, indicating that CM2A8 was the crystal that was formed. The morphological analysis (FESEM) revealed that most of the agglomerate particles synthesized by the sol–gel citrate combustion remained within the range of 50–83 nm, while the particles synthesized by the had particles as 1 μm. The specific surface area synthesized CM2A8 via the sol–gel method is in the range of 10–24 m2/g. The main advantages of the sol–gel citrate process are the high purity of the product, the narrow particle size distribution, and the achievement of uniform nanostructure at low temperatures.

Structural Elucidation, IR spectroscopy and DC electrical conductivity of Ni0.6Zn0.4GdyFe2-yO4 nanoferrites synthesized via a low-temperature citrate gel combustion method

In the present work, we report the detailed Powder XRD Rietveld refinement and elucidation of structural factors of Ni0.6Zn0.4GdyFe2-yO4 nanoferrites. The Ni0.6Zn0.4GdyFe2-yO4 nanoferrites synthesized via low-temperature citrate gel combustion technique for the various levels of Gd3+ ion concentration (y = 0.0, 0.1, 0.15 and 0.20). The generated structural factors signify the dependence on the concentration of Gd3+ ions. The prepared samples were found to crystallize in the Fd-3m space group and also identified their occupancies; some of the Fe3+ ions of the octahedral site at the 16d position will be replaced by Gd3+ ions. The lattice constant and crystallite size dropped to a low value for y = 0.1, and then, later, noticed the small increment. The crystallite sizes of the sample are to fall in the range of 26.1 nm–37.6 nm. The cation distribution among the tetrahedral (AII) and octahedral sites (BII) has been estimated. The obtained values correlate with Gd3+ ion concentration, and the radius variation of AII and BII sites signifies the migration of Fe3+ ions from the BII site to the AII sites. The force constant of Metal-Oxygen bonds was determined from the infrared spectrographs; the force constant was found to be relatively low with the BII site. The DC electrical conductivity infers the semiconducting nature and distinct phase of conductivity, which is attributed to the magnetic phase change due to temperature. The magnetic curie temperatures of the sample are obtained by the Arrhenius plot, which signifies the dependence of Gd3+ion concentration.

The study of structural, frequency and temperature dependence of electrical and dielectric properties of CuO-substituted Ni-Zn nanocrystalline ferrites for MLCI applications

ABSTRACT The Cu2+ ion-substituted Ni-Zn ferrites were synthesised by the citrate gel auto-combustion method. The structural and micro-structural analyses of all samples were done using XRD and SEM, respectively. XRD studies confirmed that all samples belong to a cubic spinel structure. The cation distributions of all samples were estimated using relative X-ray intensity calculations. Room temperature, temperature variation, electrical resistivity, initial permeability and dielectric properties were carried out by an impedance analyser. The dielectric and permeability values decreased with increasing frequency. The addition of Cu2+ ions in the present system modifies the cation distribution which results in a gradual decrease of magnetisation values. The temperature dependence of initial permeability showed a sharp decrease with increasing temperature. This indicates the formation of a single phase of materials. The maximum permeability value obtained at x = 0.10 is directly related to the grain size. These temperature variation studies indicate that all these materials are well-suitable for MLCI applications.

Rare Earth Nd3+ Doping Cobalt-Cadmium Nanoferrites Structural, Optical, and Magnetic Properties and Applications

Nanoscale particles of neodymium-substituted cobalt-cadmium generic formula for nanoferrite Co0.4Cd0.6NdxFe2−xO4 samples at X = 0.000, 0.003, 0.005, 0.007, 0.009, and 0.011 were studied. The prepared powders were synthesised at low temperatures using citrate gel auto-combustion process. The synthesised powders were calcined at 500 °C for four hours. The morphological properties of the sintered powders were investigated, and their crystal structure was determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD peaks confirmed the spinel ferrite structure. The lattice parameter was calculated from the XRD and showed decreasing trends with 8.442 to 8.308. SEM revealed an irregularly-shaped grain morphology with a homogeneous distribution. Raman spectroscopy analysis showed slight frequency changes in the Raman modes in doped samples, attributed to variations in the cation distribution. The peaks are located at 191, 291, 461, 591, and 671 cm−1. UV spectroscopy studies showed that the energy band gap values decrease with increasing Nd3+ concentration. Direct optical band gap values obtained were 1.238, 1.248, 1.199, 1.135, 1.134, and 1.101 eV with increasing Nd doping. The magnetic hysteresis properties were determined using a SQUID-VSM magnetometer. The hysteresis curves of Co0.4Cd0.6NdxFe2−xO4 nanoparticles show an increase in coercivity with increasing doping concentration. This enhancement is attributed to the multi-domain behaviour.

Composites of Zn-Co spinel ferrites and PANI: Structural, magnetic, microwave absorption characterization in 18–40 GHz

The present research work deals with the fabrication of composites containing spinel ferrites and polyaniline as high-performance microwave absorbers. The composites were prepared by the inter-mixing of Zn-Co spinel ferrites and PANI polymer in a 4:1 M ratio using the mechanical blending technique. The sol–gel citrate route was employed to synthesize Zn-Co spinel ferrites, while the oxidative polymerization method was used to synthesize PANI. The structural, morphological, magnetic, and microwave absorption properties of the composite samples were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), and vector network analyzer (VNA), respectively. The X-ray diffraction patterns indicated the crystalline nature of spinel ferrites and the amorphous nature of PANI. The magnetic properties revealed that saturation magnetization (Ms) increased significantly with the addition of spinel ferrites into PANI owing to its magnetic nature. The microwave absorption results showed that the minimum reflection loss (RL) reached up to −26.63 dB at 20.72 GHz with the effective bandwidth of 5.95 GHz in the K-band and −39.16 dB at 35.68 GHz with the effective bandwidth of 8.1 GHz in the Ka-band for composition NZP. This study indicated that the prepared SF/PANI composites can be proposed as a promising absorbent in the K-band and Ka-band.

Eu3+ Doped CoFe2O4 Nanoparticles with XRD and FTIR Analysis

Pure and Eu3+ doped cobalt ferrite nanoparticles with the formula CoEuxFe2-xO4(x = 0.00,0.10) were synthesized by citrate gel auto combustion method. X-ray diffraction analysis validated both the phase formation and purity of the synthesized nanoparticles. The Fourier-transform infrared (FTIR) spectra of the sample were meticulously recorded within the spectral range of 200-1000 cm^-1. This analysis provided insights into the formation of the spinel structure.

Structural and Electrical Properties of Li Substituted Mg Nano Ferrites: Prepared by Citrate-gel Auto Combustion Method

LixMg1−xFe2O4 where x=0.0to0.5with0.1 nano ferrites were synthesized by citrate gel auto combustion. Using a field-emission scanning electron microscope (FE-SEM) and the X-ray diffraction technique, their structural and topographical studies were examined. The prepared nano ferrites’ single-phase cubic spinel along the Fd3m space group is confirmed by the structural investigation. The synthesized samples were found to have a crystalline size of 20–26 nm, as determined by the Debye–Scherrer formula. Lattice parameter variation observed for the samples indicates dopant atoms into a crystal lattice can also lead to changes in the lattice constant. FE-SEM images revealed the clear grain and grain boundaries with agglomerated structure and it varied between 33.6 nm-24.4 nm. Two bands observed in Fourier transform infrared spectroscopy illustrates the M-O band in tetrahedral and octahedral sites. Dielectric parameters of the sample observed by LCR meter. Single semicircle behavior observed in impedance spectra. Dielectric constant and dielectric loss decreased as increasing frequency explained by Koop’s theory of mechanism. AC conductivity increasing trend observed with frequency, mobility of charge carrier active at high frequency domain.

Rare earth Gd3+-substituted Co spinel nanoferrites structural, dielectric and magnetic properties

Gadolinium-doped cobalt ferrite CoGdxFe2-xO4 (CGF) were produced using citrate gel auto-combustion method (x = 0–0.025 at an interval of 0.005). An investigations on the impact of Gd3+ ions on structural, dielectric, and magnetic properties were conducted. The synthesized materials were characterized using the following techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, ultraviolet visible spectroscopy (UV), impedance (dielectric) analysis, and vibrating sample magnetometer (VSM). The crystalline size ranging from 48 to 13 nm. The Williamson-Hall plots were utilized to examine the impact of crystalline size and lattice strain on the peak broadening of each sample. The X-ray diffraction spectra were used to confirm phase identification and spinel structure. The results of FTIR examinations show that strong metal oxide bonds can be found in the tetrahedral and octahedral sites at wavelengths of 351–376 cm−1 and 567–574 cm−1, respectively. The obtained samples to study optical energy bandgap (Eg), which vary from 2.01 eV to 2.45 eV and show that they are semiconducting materials.The Maxwell-Wagner model and Koop's theory have both been used to study the behaviour of dielectric properties. The dielectric constant at room temperature to 673 K in the frequency range 50 Hz–1 MHz to study the dielectric constant, dielectric loss, AC electrical conductivity, and impedance. The impedance charts show how conductivity was impacted by grain and grain boundary mechanisms. In relation to an applied field of 100 kOe, magnetization was measured at 3 K and 300 K. The blocking temperature (TB), which exhibits super-paramagnetic behaviour, is found to be approximately 359 K according to zero-field cooling ZFC and field cooling. The FC experiments carried out in the temperature range of 3 K–360 K under an applied field of 100 Oe.

Synergizing experimental and theoretical insights: Unveiling the solar potential of La2NiMnO6 double perovskite for enhanced efficiency and sustainability in photovoltaics

Amidst the escalating demand for sustainable energy solutions, this research delves into the competence of double perovskite oxide La2NiMnO6 as a solar cell luminary. Addressing material synthesis, structural intricacies, and device construction, the study responds to the limitations of labour-intensive first-generation Si solar cells along with the toxicity of lead attributed perovskite solar cells, steering towards a revolutionary era. La2NiMnO6 distinctive attributes a formidable dielectric constant, positioning it as a beacon in solar energy. Crafted via sol gel citrate alchemy, its structural, optical, and electronic intricacies were meticulously explored. Experimental insights into the fabrication process, employing optimised spray pyrolysis layers, enrich the narrative. Structural analyses confirm La2NiMnO6 prowess, while optical studies unveil its visible spectrum absorbance. Simulations and the experimental J-V curve show PCEs of 10% and 4.5 %, solidifying the La2NiMnO6 stance in the all-inorganic perovskite solar cell realm. This study propels the evolution of photovoltaic technology, laying pathways for sustainable energy alternatives and setting new benchmarks.

Synergistic integration of rGO into cobalt oxide matrix for efficient electrochemical performance mediated by structural stability

The growing global challenges have prompted researchers to create efficient energy production and storage tools. In our quest to find optimal electrode materials for supercapacitors to meet energy demands, we embarked on an intriguing journey with electrochemically efficient Co3O4 composites integrated with reduced graphene oxide (rGO) in various wt% (5 %, 10 %, and 15 %). The citrate–gel auto-ignition approach was employed to synthesize Co3O4, followed by the solvothermal technique for Co3O4/rGO composite formation. Structural characterization through X-ray diffraction unveiled the spinel cubic crystallinity of Co3O4 and exposed a reduction in crystallite size with the addition of rGO. Morphological features examined by field emission scanning electron microscope revealed small grain size and porosity variation directly influenced by varying rGO concentrations, while energy dispersive X-ray confirmed the existence of different constitutional elements. The comprehensive electrochemical analysis confirmed the pseudocapacitive nature of as-synthesized electrodes via cyclic voltammetry in a 2 M KOH solution. Meanwhile, galvanostatic charge-discharge displayed CO-III has a maximum specific capacitance (1478 Fg−1), energy (74 Whkg−1), and power densities (0.90 kWkg−1) with 83 % retention at 3 Ag−1 suggesting its potential suitability for supercapacitor applications.

Structural characterization, optical, and magnetic properties of MgTbxFe2−xO4 nano ferrite particles using a combustion technique

The citrate gel auto-combustion method was utilised to synthesis terbium-doped nanoparticles (NP) with considerable concentrations of magnesium ferrites, using the chemical formula MgTbxFe2−xO4 and an X range of 0.000 to 0.0030 (with an X step of 0.0005). At 300 K, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transition electron microscopy (TEM), and magnetic characteristics were all determined. The XRD and TEM images indicate nanoscale ranges as well as the cubic spinel structure, which is merely phased, and confirm the normal crystallite size. The lattice parameter and volume decrease as density increases with doping of terbium. The images from the FESEM. It is evident that the grain clusters were found within the material. In the specimen's case, the highly interacting grains were found. The fourier-transformed infrared spectroscopy (FTIR) data clearly suggests that two metallic bands have formed, confirming the cubic spinel ferrites. There are two primary absorption bands visible between 200 and 650 cm−1. The UV–vis investigation demonstrates that the calculated direct band gap energy values have a violet shift. The band gab energy was reported in the range of 415.30 eV to 375.12 eV.The magnetic properties of the hysteresis loops indicate a transition from hard magnetic moments to soft magnetic moments. All magnetic properties were reduced when the Tb3+ ion was substituted. They are excellent for switching memory storage devices as well as telecommunications.

Rare earth Gd3+ substituted on cobalt ferrites: Structural and dielectric studies by citrate gel autocombustion method

Gadolinium-doped cobalt ferrite (CoGdxFe2-xO4; X = 0–0.025 in a 0.005 interval) was synthesised using citrate gel autocombustion. The effect of Gd3+ ions on structural, dielectric, and magnetic characteristics has been investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, ultraviolet visible spectroscopy (UV), an impedance (dielectric) analyzer, and a vibrating sample magnetometer (VSM) were used to characterise the as-synthesised materials. X-ray diffraction powder patterns were used to confirm phase identification and spinel structure, and the Williamson-Hall plot was used to investigate the crystalline size and lattice strain on the peak broadening of each sample, with crystalline size ranging from 13 to 48 nm. The scanning electron microscopy (SEM) micrographs demonstrate particle agglomeration, while energy dispersive spectroscopy (EDAX) pictures indicate the purity and existence of all elements in the created material samples. The frequency-dependent dielectric constant, dielectric loss, and AC electrical conductivity in the frequency range 50 Hz–1 MHz. The behaviour of dielectric properties has been studied using the Maxwell-Wagner model and Koop's theory. Because of this, higher frequencies show less dielectric loss, making them appropriate for use in high-frequency device applications.

Improvement of the Self-Controlled Hyperthermia Applications by Varying Gadolinium Doping in Lanthanum Strontium Manganite Nanoparticles

In this study, silica-encapsulated gadolinium was doped in lanthanum strontium manganite nanoparticles (NPs) with different concentrations using the citrate–gel auto-combustion method. We focused on tuning the Curie temperature and enhancing the specific absorption rate (SAR) of silica-coated gadolinium-doped lanthanum strontium manganite NPs to make them suitable for self-controlled magnetic hyperthermia. The samples were characterized by using transmission electron microscopy (TEM), X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and magnetic measurements to examine the structural, optical, and magnetic properties of the manganite NPs. While our results exhibit a successful doping of gadolinium in lanthanum strontium manganite NPs, we further prepared magnetic core NPs with sizes between 20 and 50 nm. The Curie temperature of the NPs declined with increasing gadolinium doping, making them promising materials for hyperthermia applications. The Curie temperature was measured using the magnetization (M-T) curve. Magnetic heating was carried out in an external applied AC magnetic field. Our present work proved the availability of regulating the Curie temperature of gadolinium-doped lanthanum strontium manganite NPs, which makes them promising candidates for self-controlled magnetic hyperthermia applications.

The Comparison Between The Effect of Different Medical Drugs used To Improve Endometrial Receptivity in patients with Thin Poorly Vascularized Endometrium

In a perfect world, the peak of receptivity of the endometrial lining would occur simultaneously with the entry into the uterine cavity of a healthy blastocyst, which would then be able to adhere, attach, invade, and develop protected until the time of delivery. This would be the ideal scenario. The study was carried out on 200 infertile women who have thin , poorly vascularized endometrium, those patients were divided into five groups ; 40 patients in each group, group A received esterofem oral, group B received vagifem vaginal tablets, group C received sildenafil citrate gel, group D received pentoxifylline oral and group E received 4 grams of pentoxifylline vaginal gel. The endometrial thickness, vascularity zones, sub endometrial flow, and both uterine arteries resistance and pulsatility indices were assessed at the middle of the menstrual cycle (day 11–14) on a monthly basis for six cycles or until a positive pregnancy test was obtained. Pentoxifylline vaginal gel, pentoxifylline+ vitamin E capsule, and sildenafil vaginal gel have improved the vascularity indeces of endometrium and uterine arteries, while the vagifem and esterofem were less effective in terms of improving the vascularity indeces of endometrium and uterine arteries. The study also showed that 57.5% of women succeed to get pregnant after six months of receiving pentoxifylline vaginal gel, 35% of women succeed to get pregnant after six months of Pentoxifylline+vit E, while 22.5% of women succeed to get pregnant after six months of sildenafil, about 10% of women got pregnant after six months of vagifem, and finally 2.5% of women got pregnant after six months of receiving estrofem tablets. It was discovered that pentoxifylline vaginal gel, pentoxifylline tablet plus vitamin E capsule, and sildenafil vaginal gel were able to improve the vascularity index of the endometrium, the uterine arteries and endometrial thickness, and enhance the pregnancy rates in patients with thin poorly vascularized endometrium

Cu-Doped SrTiO3 Nanostructured Catalysts for CO2 Conversion into Solar Fuels Using Localised Surface Plasmon Resonance

Carbon dioxide valorisation is one of the most discussed topics amongst researchers; indeed, finding a way to significantly reduce CO2 concentration in the atmosphere is crucial in order to mitigate climate change effects in the next decades. In this study, SrTiO3-supported Cu nanoparticles are exploited as Localised Surface Plasmon Resonance (LSPR)-mediated catalysts for CO2 reduction. The materials were prepared via sol–gel citrate route methodology, inserting Cu as a dopant in the perovskite structure; reducing treatments at different temperatures were performed to promote copper atom exsolution, thus forming nanostructures upon the surface. The perovskitic structure was confirmed via ex situ and operando XRD analysis, while compositional analysis was carried out through XPS and EDS; SEM and TEM images revealed morphological changes with different reducing treatments, and bulk reducibility was analysed with H2-TPR, revealing different Cu species in the material. Band gap analysis via DRS showed the successful incorporation of copper in the perovskite, affecting the light absorption properties. Finally, catalytic tests showed that copper nanoparticles play a role in CO2 activation with sunlight, proving that LSPR could be exploited for catalytic means.

Fast switching capability and efficient magneto-electric coupling mediated by tunable ferroelectricity and magnetization in tri-phase composites for ultra-sensitive devices

Tri-phasic multiferroic composites exhibiting simultaneous magnetic and electric orderings and their coupling, have emerged as a fascinating class of materials for enriched magnetoelectric response that could be feasible for next-generation multistate devices. Such attributes are further triggered by facile synthesis routes and proper selection of phase contents. Herein, a composite series of the form, 0.9[(1–x)BiFeO3 + xCoFe2O4] +0.1Pb(Zr,Ti)O3 (x = 0.0, 0.2, 0.3 and 0.4) was synthesized via citrate–gel based auto-ignition and solid–state reaction routes. The phase-pure existence of spinel phased CoFe2O4 and perovskite textured BiFeO3 and Pb(Zr,Ti)O3 was confirmed by X-ray diffraction and Rietveld’s refinement, while the stoichiometric contents of three phases were verified by energy dispersive X-ray spectroscopy. The optimized ferroelectric parameters demonstrated an enhancement in polarization by increasing substitutional contents and maximum polarization (0.22 µC/cm2) was observed for x = 0.4 phase fractions. Magnetic hysteresis loops revealed increased magnetization as CoFe2O4 phase-fractions were increased signifying maximum magnetization (Ms = 20.41 ± 0.02 emu/g) for x = 0.4 substitution contents. The findings revealed that x = 0.4 composition was a potential candidate for emerging ultra-fast electric and magnetic energy storage devices.

Silver substituted cobalt zinc ferrites as magnetic antimicrobials

Silver-substituted cobalt zinc ferrite series, CoxAg0.5-xZn0.5Fe2O4 (x = 0.4, 0.3, 0.2, 0.1), is synthesized using the citrate gel method, wherein ferrite formation is achieved at 600 °C. The low-temperature crystallization results in agglomerated and porous ferrites. In this sample preparation methodology, as the silver content in the series increases, metallic silver deposits at the grain boundaries, and vacancies are created at the octahedral sites. With a further increase in silver content, the magnitude of magnetic properties decreases. Antimicrobial activity increases and further decreases with an increase in silver content. The composition Co0.4Ag0.1Zn0.5Fe2O4 exhibits both magnetic and antimicrobial behaviour. These materials can potentially be beneficial in the manufacture of removable antimicrobial agents for water purification and drug delivery systems.

Magnetocaloric properties of TbCrO3 and TmCrO3 and their comparison with those of the other RCrO3 systems (R = Gd, Dy, Ho, and Er)

Magnetocaloric properties of TbCrO3 and TmCrO3 are reported and compared with those of the previously reported rare-earth chromites RCrO3 (R = Gd, Dy, Ho, and Er) and other perovskite-type oxides. The samples of TbCrO3 and TmCrO3 in this work were synthesized using a citrate gel combustion technique, and their magnetic properties were investigated and compared with those reported previously on RCrO3 (R = Gd, Dy, Ho, and Er). The Cr3+–Cr3+ ordering temperatures were found to strongly depend on the ionic radii of the rare-earth. By fitting the dc magnetization data with modified Curie–Weiss law including the Dzyaloshinsky–Moriya antisymmetric exchange interaction (D) and the symmetric exchange constant Je, spin canting angles (α) were obtained. In general, α was found to increase with the decreasing ionic radii of R3+ in RCrO3. The magnetocaloric properties investigated included the magnetic entropy change (−ΔS) for a given change in magnetic field (ΔH), the corresponding adiabatic temperature change (ΔTad), and their relative variations (ΔTad/ΔH) and (−ΔS/ΔH). It is observed that for RCrO3, (−ΔS) measured in the vicinity of the ordering temperature of R3+–R3+, varies almost as G2/3 where G is the de Gennes factor. Among RCrO3, GdCrO3 shows the largest value of (−ΔS/ΔH), because of its largest G factor and its magnitudes of (ΔTad/ΔH) and (−ΔS/ΔH) compare well with the reported values for the perovskites GdFeO3 and EuTiO3. These comparisons presented here provide useful information on the potential use of these materials in magneto-refrigeration technology.