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The synthesis of zinc-substituted cobalt ferrite (Co0.9Zn0.1Fe2O4) using the sol gel method has been successfully carried out. The thermogravimetric analysis and differential thermal analyzer curve shows that at 400°C the Co0.9Zn0,1Fe2O4 sample has formed the final phase of nanoparticles. Therefore, the modification of physical properties was carried out by annealing treatment at temperature of 450°C, 550°C, 650°C, and 750°C. The X-rays diffraction show that all samples are in a single phase with a face center cubic space group Fd-3m structure according to the ICDD 221086. The crystal size increased with the annealing temperature 33.69 nm to 45.88 nm. The Co0.9Zn0.1Fe2O4 showed as excellent antibacterial properties on Staphylococcus aureus and Escherichia coli. The most superior antibacterial activity to Staphylococcus aureus was Co0.9Zn0,1Fe2O4 sample which was annealed at 650°C with a clear zone diameter of 39.81 mm. Meanwhile, the Escherichia coli bacteria which had the most superior antibacterial activity were Co0.9Zn0,1Fe2O4 samples which were annealed at 450°C with a clear zone measuring 21.04 mm.

Lanthanum-substituted cobalt ferrite nanoparticles (CoLa0.1Fe1.9O4) with different Fe3+ cation sources i.e., using standard chemical lab (sample A) and a Bengawan Solo River fine sediment (sample B), were synthesized using the co-precipitation method. FTIR analysis showed that the absorption of the two nanoparticles sample appeared at a peak of v1=586.39 cm-1, whereas the v2 appear at 461.97/cm and 435.93/cm respectively. It is suggested that the La3+ cation has succeeded in replacing the original structure of the cobalt ferrite. X-ray diffraction analysis showed that nanoparticles produce using a standard chemical lab (sample A) have smaller crystallite sizes, D=18.16 nm than the natural source of fine sediment (sample B), D=24.56 nm, respectively. Furthermore, the VSM results showed that the magnitude coercive field of Hc = 3100 Oe and Hc = 100 Oe for samples A and B, respectively. Meanwhile, the obtained saturated magnetization Ms of 15.55 emu/g for sample A and the Ms is 58.40 emu/g for sample B. This result informs that if a hard magnetic material is desired then the use of lab raw materials is more promising, while if soft magnetic is desired then a natural source of fine sediment is more appropriate to use.

The annealing temperature dependent on the structural and magnetic properties of hematite (α-Fe2O3) powders synthesized via the sol-gel method was studied. The sol-gel method is used to prepare nanoparticles for this experiment. The annealing treatment of 200°C, 400°C, 600°C, and 800°C has been carried out to modify the physical properties. The obtained nanoparticles are characterized by their structural properties using X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Then, magnetic properties were evaluated using Vibrating Sample Magnetometer (VSM). XRD results have shown an increase in crystallite size with an increase in annealing temperature from 35.10 nm to 60.17 nm. The increase in crystallite size can be attributed to the increase in the crystal structure’s internal energy, which promotes atomic diffusion. The FTIR results show an absorption that appears at the peak around ~530 cm-1. It indicates that the Fe3+ cation has successfully formed. The VSM results show an increase in the value of Hc with an increase in the annealing temperature from 117 Oe to 461.5 Oe. It is supported by the increase of anisotropy constant and increasing temperature annealing.

The effect of annealing temperature on the structural and magnetic properties of a rare earth (La3+) doped cobalt ferrite with fine sediment from the Bengawan Solo River as the source of Fe3+ has been studied. Co-presipitation method is use for preparation nanoparticles whole this experiment. In order to modified the physical properties, the annealing treatment of 2000C, 3000C, and 4000C are performed. The obtained nanoparticles are characterized their structural properties by using X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Then, magnetic properties evaluated by using Vibrating Sample Magnetometer (VSM). XRD results have shown that there is an increase in crystallite size with an increase in the given annealing temperature from 24.56 nm to 27.83 nm. The increase in crystallite size can be attributed to the increase in the internal energy of the crystal structure which promotes atomic diffusion. Meanwhile, there is a decrease in the value of the lattice parameter with an increase in the given annealing temperature. The decrease in lattice parameters with increasing crystallite size is generally due to the lattice parameters reaching a minimum energy with increasing crystallite size. The formation of La3+-O2- for the incorporation of rare earth ions into the lattice requires high energy. The FTIR results show an absorption that appears at the peak around ~580 cm-1. This indicates that the La3+ cation has successfully replaced the original structure of cobalt ferrite. The VSM results show that there is an increase in the value of Hc with an increase in the annealing temperature given from 100 Oe to 160 Oe. This is supported by the increase of anisotropy constant and increasing temperature annealing.

Single-domain configuration is one of the important key in the applied current- technology especially information technology. In order to address this issue, a magnetic modification of cobalt ferrite nanoparticles (CFO-NPs) by decorating the monazite-natural-mineral (Ce) is presented. Monazite-decorated CFO-NPs are successfully synthesized by the co-precipitation method. The obtained nanoparticle samples are annealed at 200 °C, 300 °C, and 400 °C for 5 hours. XRD results confirms the successful decoration of the monazite sand with CFO-NPs, as demonstrated by the distinctive peaks of CFO-NPs, as well as the major peaks of the monazite-sand. The presence of monazite in the CFO-NPs sample was confirmed by the EDS results. With increasing annealing temperature, the crystallite size increases, respectively. FTIR results show that the monazite-decorated CFO-NPs outcome absorption peaks at kt∼590/cm and ko∼390/cm, which are the original absorptions of CFO-NPs. VSM results showed that the single-domain configuration realized owing high the HC(supported by K1and Kσ) for samples without and annealed at 200 °C, whereas the multi-domain configuration appears to have a small HC(supported only by K1) for samples annealed at 300 °C and 400 °C. The largest HCof the monazite-decorated CFO-NPs was obtained with the annealing temperature at 200 °C, i.e., 3.02 kOe, suggesting that it be supported by both the K1and Kσ. The magnetic properties obtained also indicate the potential for developing permanent magnets.

Modification of nanometer size order in anode material of hematite nanoparticles is believed to be one of the keys to increasing the specific capacity of Li-ion batteries application. So that, the synthesis temperature dependence of nanocrystallite size properties in co-precipitated hematite nanoparticles is studied. Sample of Hematite nanoparticles is modified the physical properties by synthesis temperature and then annealed of 700°C for 4 hours. The crystallite size increase with the increase of the synthesis temperature i.e., 23.06 to 29.64 nm. It is indicated that the synthesis temperature affects crystallite formation. Furthermore, the magnetic properties show that the coercive field decrease from 869 to 211 Oe with the increase of the temperature synthesis. It is related to the change in the nanosize-order of the sample crystallite.

Graphical Abstract:

We report change in the structural and the magnetic properties of a gamma-irradiated sample of CoBi0.1Fe1.9O4nanoparticles synthesized using the co-precipitation method. All samples were exposed to low doses of γ-radiation (i.e., 0, 100, 200, 400, and 800 Gy). The X-ray diffraction (XRD) evaluations indicated that all samples had a single-phase cubic spinel structure in space group Fd3m. The crystal size, lattice parameter, and other structural parameters of the irradiated CoBixFe2-xO4nanoparticles were calculated based on the XRD data. The crystallite size is found to increase with increasing radiation dose. The stretching vibration modes of the absorption bands (v1and v2) were observed in the Fourier transform infrared (FTIR) spectrum, thereby reconfirming that the metal oxide is realized a cobalt ferrite-based material. The change in the surface morphology was measured using scanning electron microscopy (SEM). Finally, the modified magnetic parameters (Hc, Ms, Mr) of the gamma-irradiated samples were determined from the M–H loop recorded at room temperature.

Influence of gamma irradiation to the magneto-impedance ratio of the electrodeposited [NiFe/Cu]4 multilayer on meander-shape PCB substrate has been studied. The magneto-impedance ratios were measured for both un-irradiated and irradiated by gamma radiation of Co-60 with a total dose of 40 Gy. The morphological structure were done by using scanning electron microscopy (SEM). The decrease in grain size of the samples after Gamma irradiated is observed. The magnetic property modifies as consequence of the change in the microstructure samples. Within result, the magneto-impedance ratio decreases around 34.9% for irradiated sample.

Magneto-impedance ratio of the multilayer [NiFe/Cu)]N study by the number of multilayer. The both sample films of NiFe and Cu are fabricated by electrodeposition methods on a Cu-patterned substrate. The characteristic of magneto-impedance (MI) is performed at room temperature. Magneto-impedance are modified by varying N times (2, 4, 6 and 8) and the measurements frequency. The result show that the typical symetry of the magneto-impedance curve. Then the magneto-impedance (MI) ratio increases with the increase of frequency and N number layers. The increase of the magnetic permeability should address the increase of the MI ratio. Finally, the highest magneto-impedance ratio of 13.79 is obtained for [NiFe (200)/Cu (25)]8 at frequency 100 kHz.

Increasing dispersion stability is the main issue in recent research at magnetorheological (MR) fluids. The presentation of nanoparticle addictive in MR fluids is an effective method not only to increase dispersion stability but also increasing performance in MR fluids. In this study, the effect of hard magnetic CoFe2O4 nanoparticles addition on rheological properties and dispersion stabilization had been studied. Rheological properties were investigated using a rheometer at room temperature. The result showed that the addition of CoFe2O4 nanoparticles 1wt% in particles of MR fluids were improving the shear stress and viscosity of MR fluids. Both MR fluids with and without nanoadditives behaving like a Newtonian fluid at the off-state condition and act like Bingham fluid at the on-state condition. Moreover, MR fluid with CoFe2O4 additives had a higher sedimentation ratio than MR fluids without additives.

In this study, the synthesis of CoFe2O4 by using the fine sediment of the Bengawan Solo River, Trucuk District, Bodjonegoro Regency as raw materials with the coprecipitation method has been successfully carried out. The fine sediment is used as a source of Fe cation in the synthesis of CoFe2O4. The XRD confirmation results showed that CoFe2O4 is formed at an annealing temperature of 800° C with crystallite sizes ranging from 34.88 to 38.05 nm. Thus, the VSM characterization showed that the magnetic properties of the CoFe2O4 nanoparticles depend on the heat treatment of the fine sediments as ore materials. Finally, the obtained CoFe2O4 samples can be used as photocatalysts with a maximum reduction rate ratio of 83%.

Comparison of the crystalline structure and magnetic properties in CoFe2O4 and CoLa0.1Fe1.9O4 nanoparticles have been studied. The obtained samples are characterized by using X-Ray Diffractometer (XRD), Fourier Transform InfraRed (FTIR) and Vibrating Sample Magnetometer (VSM). The XRD results show that the crystallite size of the samples are 24.539 nm and 28.772 nm for the CoFe2O4 and CoLa0.1Fe1.9O4 nano particles, respectively. Furthermore, the crystalline strain is 0.00460 and lightly decreases to 0.00392 with the presence of lanthanum. The different of the atomic radius for both Fe3+ (1.26 Å) and La3+ (1.87 Å) should attribute to the change of the crystalline strain. FTIR results show that the absorption peak of the CoFe2O4 occur at k = 591.21/cm and the CoLa0.1Fe1.9O4 is 594.10/cm. This indicate that the lanthanum cation successfully substitutes to the original bonding-structure of the CoFe2O4. VSM results show that the HC are 1.02 kOe and 0.705 kOe for the samples without and with La3+ cations. Moreover, the MS is equal 69.625 emu/g and decrease of 55.70 emu/g with the present of the La3+ cations. Finally, the strains-induce-magnetism should contribute to the changes of the MS that associated with changes in crystalline strains at the previous discussion.

The synthesis of CoBi0.15Fe1.85O4 obtained from cobalt ferrite doped by bismuth using the coprecipitation method was successfully carried out by varying the temperature of the titration. In this study the temperature of titration was used at 65°C, 75°C, 85°C, and 95°C. Annealing was then carried out at a temperature of 800°C for 5 hours. The results of the synthesis were then characterized using X-Ray Diffractometer (XRD), Fourier Transform Infra-Red (FTIR) and Vibrating Sample Magnetometer (VSM). The increase of the magnetic characterization i.e. the saturation magnetization increases and coercivity attribute the increase of the anisotropy crystalline.

This study aims to prepare strontium-substituted cobalt ferrite (Sr0.1Co0.9Fe2O4) nanoparticles by using a simple co-precipitation process followed by annealing at 300°C–600°C for 5 h. The Sr0.1Co0.9Fe2O4nanoparticles thus obtained have a face-centred cubic (fcc) inverse-spinel crystalline structure with crystallite sizes in the range from 17.26 to 26.97 nm. The saturated magnetization of the nanoparticles increases with increasing annealing temperature. Furthermore, the transition from a multi-domain to a single-domain configuration is investigated from the viewpoint of the dependence of the crystallity on the coercive field.

The effects of the synthesis temperature on the crystalline structure and the magnetic properties of cobalt ferrite (CoFe2O4) nanoparticles prepared via coprecipitation are discussed. The synthesis was conducted at temperatures of 75 °C, 85 °C and 95 °C. Fourier transform infrared spectroscopy characterization related to a stretching vibration at a wavenumber of 590 cm−1indicated the formation of a CoFe2O4metal oxide. In addition, powder X ray diffraction (XRD) characterization proved that the metal oxide was CoFe2O4. Crystallite sizes calculated using the Scherer formula at the strongest peak of the XRD spectra of the samples synthesized at 75 °C, 85 °C and 95 °C were 32 nm, 43 nm and 50.4 nm, respectively. Finally, the results of the vibrating sample magnetometer characterization showed that the saturation magnetization decreased with increasing synthesis temperature, which is related to the dominant preference of Co2+over Fe3+cations at the octahedral sites.

Synthesis and fabrication of nanoparticle-based thin layer of natural porphyrin was reported in this paper. The natural porphyrin solutions used in the experiments were synthesized by using a process of column chromatography techniques. Then natural porphyrin thin films were deposited by spin coating methods on Cu substrate. Experiment result showed that natural porphyrin thin films composed of discrete islands. More detailed observation show that the islands were formed from smaller islands that called supra molecule.

We present magneto conductivity measurements in natural porphyrin thin films in magnetic fields of 100 Oe at room-temperature. The films used in this experiment were isolated from natural spirulina sp by chromatography procedure with n-hexane. Each layer fabricated by spin coater methods with rotation speed of 2500 rpm for 60 second is followed post heating at temperature of 60°C for 300 second. The procedure is repeated N times. Magneto-conductance effect is presented at room temperature with induce magnetic field in plane of films. The results show that ratio magneto-conductance decreases with the increase of voltage provided. The magneto-conductance ratio increase with the increase of N repetition number. Finally, both the results indicate that magneto-conductance effect could be realized due to annihilation of carrier charge.

Bio-impedance based sensor using organic polymer-membrane was presented in this paper. The Ca-alginate with glycerol as plasticizer used in the experiments was fabricated by slip casting method on a glass substrates. After atmospheric heating treatment of edible films at 60°C for 24 hours, the films-membranes of 50 mm were obtained. Bio-impedance characterizations were carried out by LCR meter at room temperature. The experiment results showed that the sensor finely operated at low frequency i.e. less than 40 kHz. Response of the sensor increased with the increase of samples mass and became constant after a critical mass. Finally, bio-impedance responses of beef and pork were clearly indicated by a different magnitude that it is possible to apply the films-membranes as bio-sensor applications.

Strontium-substituted cobalt ferrite nanoparticles were synthesised via the co-precipitation method. Thermogravimetric analysis (TGA) showed that the relative reduction of the mass was supported by the available strontium cations. X-ray diffraction analyses clarified that single-phase nanoparticles were obtained and indicated that the strontium cations substituted metal cations in the cobalt ferrite nanoparticle system. The crystallite size increased on increasing the annealing temperature. By contrast, the crystalline stress decreased on increasing the annealing temperature. Furthermore, the saturated magnetisation decreased with an increased annealing temperature. Finally, the annealing temperature dependence of the coercive field is shown in this paper and the highest coercive field, HC, of 2.76 kOe is obtained for Sr0.1Co0.9Fe2O4nanoparticles with an annealing temperature of 1000 °C. Here, the Sr2+cations facilitate the high value of the anisotropic magnetic realisation for the whole annealing temperature treatment.

The reusability of CoFe2O4@ZnO core–shell nanoparticles (NPs) for the photocatalytic degradation of methylene blue (MB) under UV radiation was successfully investigated. CoFe2O4@ZnO NPs with various CoFe2O4–to–ZnO concentration ratios were synthesized as magnetic photocatalysts. The X-ray diffraction spectra showed that the NPs had a cubic spinel ferrite phase structure and a hexagonal wurtzite phase of ZnO. Fourier-transform infrared spectra showed the presence of Moct-O, Mtet-O, and Zn–O at 593, 347–389, and 410–429 cm−1, respectively. The CoFe2O4@ZnO NPs had a saturation magnetization of approximately 30 emu g−1and a coercivity of approximately 280 Oe. The absorbance spectra showed that the absorbance peak of the CoFe2O4@ZnO NPs broadened and shifted to the right (higher wavelength) with increasing ZnO concentration. The CoFe2O4@ZnO NPs with higher ZnO concentrations exhibited higher photocatalytic activities and degradation rates. The enhancement of MB degradation can be attributed to the formation of an internal structure between CoFe2O4and ZnO. The degradation rate of CoFe2O4@ZnO decreased slightly after each successive recycle. The results indicated that the recycled CoFe2O4@ZnO NPs could be reused three times for photocatalytic degradation. As there is no significant decrease in the photocatalytic degradation after four successive recycles, the CoFe2O4@ZnO NPs are suitable for application in dye degradation.

Using extraordinary Hall resistance (RH) measurements, the material dependence of thermally assisted magnetization reversal (TAMR) was investigated for microstructured multilayers of [Co (0.17 nm)/Pd (0.80 nm)]Nwith N= 7 and 20, which exhibit markedly different magnetic properties. The threshold values of the external field (Hwth) necessary for controlling the magnetization direction in TAMR, obtained by direct application of a current pulse to the sample, were 220 Oe for the N= 7 and 710 Oe for N= 20 samples. The values of Hwthare found to be related to the magnetization saturation field at a critical temperature at which apparent coercivity decays.