Increase In Magnetization Values Research Articles

External oxide layers formed by the oxidation procedure in FeMnSi and FeMnSiCr shape memory alloys and their effects

Shape memory alloys are exposed to high temperatures to improve their properties and functionality. Through this process, oxidation inevitably occurs due to the presence of oxygen in the environment, which interacts with the alloying elements. Oxidation adversely affects the hardness of alloys, leading to a decline in their overall quality. In this study, the oxidation behavior parameters of FeMnSi and FeMnSi-Cr alloys and the oxide layers formed during this process were investigated in Fe-based alloys with high usage potential. Both non-isothermal and isothermal oxidation processes were applied to alloys and the oxidation parameters were determined. Subsequently, the changes in the crystal structure, microstructure, and magnetic properties of the alloys subjected to isothermal oxidation at 400-500-600-700-800 °C were investigated. It was found that the oxidation behavior of both alloys intensified with rising oxidation temperatures, as evidenced by crystal structure and microstructural analyses, which indicated deeper penetration into the alloys at elevated temperatures. Furthermore, an increase in magnetization values was noted alongside the oxidation process. A comparison of the oxidation characteristics between FeMnSi and FeMnSi-Cr alloys revealed that the oxidation parameters for the chromium doped FeMnSi alloy were comparatively lower.

Citrate precursor route for Y3+ substituted M-type Ba-hexaferrite: Synthesis, the effect of doping on structural, optical, magnetic and anti-bacterial properties

Herein, citrate precursor technology has been used in the lab to create BaYxFe12-xO19, where x = 0.0, 0.1 and 0.2. Fourier Transform Infrared and UV spectroscopy and Powder X-ray Diffraction have all been utilized to determine the structure and to confirm the phase formation.XRD confirmed the formation of hexagonal structure where lattice parameters a and c decreased from 5.88 Å to 5.81 Å and 23.19 Å to 23.17 Å, respectively, with the increase in doping concentration.Tauc plot facilitate with the values of energy gap for all the prepared samples, which is in decreasing order with increase in doping concentration for 4.48 eV–4.38 eV. An increase in magnetization value from 8.77 emu/g - 26.22 emu/g for doping of Y from x = 0.0–0.20 has been observed from magnetization versus magnetic field data taken from vibrating sample magnetometer. The main objective of this work is to study the antibacterial activity of the Y doped BaFe12O19 against gram positive Staphylococcus aureusas well as gram negative bacteria Escherichia coli. All the prepared samples have shown the antimicrobial effect at all the concentration with MIC value ranging from 0.55 to 0.80 mg/ml.Thus, the present study explores the potential applications of Y-doped Barium hexaferrites in biomedical applications.

Structural, electrical and magnetic properties of Er doped YCrO3 nanoparticles

Erbium (Er) doped perovskite YCrO3 (YCO) nanoparticles were successfully prepared by the sol-gel method. The crystal structure, optical, electrical, and magnetic properties of the samples were characterized. The effect of erbium doping was studied by Rietveld refinement analysis. UV–vis absorption data show that with the increase of doping concentration the band gap decreases. The result of electrical properties indicates that the increase of temperature dc conductivity increases and dielectric permittivity follows the modified Cole-Cole model. Ac conductivity variation with frequency has been explained by CBH (correlated barrier hopping) conduction mechanism. From the complex impedance plot, the existence of the grain boundary contribution to the relaxation in the sample can be seen. A relaxor like ferroelectric phase transition is observed at 450 K. The observation of the hysteresis loop and the increase of magnetization value by Er doping confirmed the magnetic ordering in YCO nanoparticles. Our results demonstrate the effect of Er doping on structural, electrical and magnetic properties of YCO nanoparticles which is essential for its successful device application.

Nb and Nb/Co films: Testing a new approach to determine the Co stray field and its influence on superconducting properties

Anisotropic Ginzburg-Landau model was systematically tested in NbtNb and NbtNb/Cu5nm/Co40nm (tNb = 20 and 100 nm) films. A ΔTC-parameter was defined as a temperature difference between the critical temperatures determined for in-plane and out-of-film plane field configurations (ΔTC=TC⊥C−TC∥C). The ΔTC behavior for Nb(20 nm) and Nb(20 nm)/Co(40 nm) films shows a linear increase with applied field concomitantly with the increase of magnetization values in the out-of-film plane configuration. The stray field of ferromagnetic Co layer was determined in the zero field case to be (7 ± 2) mT, while a variation ratio between the stray field and the applied field ((dBCodB) of the Co layer was calculated to be (−0.22 ± 0.02). Our results bring contributions to clarify proximity and magnetostatic effects; issues that still need to be comprehended for superconducting spin valve technological applications.

Co-Doped Rare-Earth (La, Pr) and Co-Al Substituted M-Type Strontium Hexaferrite: Structural, Magnetic, and Mossbauer Spectroscopy Study

The present study investigates the influence of La3+ and Pr3+ doping on the structural, magnetic properties, and hyperfine fields of Sr0.7RE0.3Fe12-2x CoxAlxO19, (RE: La3+ and Pr3+, x = 0.0 - 0.8) hexaferrite compounds prepared via auto-combustion technique. The XRD analysis shows a linear decrease in a and c lattice and unit cell volume contraction with the content x. The room temperature magnetic study shows that for the Pr3+ doped Sr0.7Pr0.3Fe12-2x CoxAlxO19 (Pr3+-SrM), the magnetization value monotonically decreases while for La3+ doped Sr0.7La0.3Fe12-2xCoxAlxO19 (La3+-SrM) magnetization value shows a noticeable increase in magnetization value with x. The coercivity of the Pr3+-SrM compound was observed to decrease while that of the La3+-SrM compound showed a marked 40% increase at x = 0.2 (~5829 Oe) in comparison to undoped SrFe12O19 (~3918 Oe). A difference in Curie temperature was also observed, with Tc ~ 525°C at x = 0.4 for Pr3+-SrM and Tc = 505°C for x = 0.4 for La3+-SrM compound. The observed differences in magnetic properties have been explained on the basis of the site occupancy of Co2+ and Al3+ in the presence of rare-earth ions. The presence of non-magnetic rare-earth ion, La3+, improved saturation magnetization, and coercivity and deemed suitable replacement for Sr2+. The hyperfine parameters namely quadrupole shift showed a decrease with the La3+ or Pr3+ doping independent of (Co2+-Al3+) ions doping. Overall, the Mossbauer analysis suggests that the (Co2+-Al3+) impurities prefer occupancy at 2a site.

Structural and magnetic properties of nanosized CoxZn(1-x)Fe2O4 (x= 0.0, 0.5, 1.0) synthesized via autocatalytic thermal decomposition of hydrazinated cobalt zinc ferrous succinate

Nanocrystalline monophasic cobalt substituted zinc ferrite with general formula CoxZn(1-x)Fe2O4 (x = 0.0, 0.5, 1.0) were synthesized by precursor combustion method. The precursors namely, hexa-hydrazine cobalt zinc ferrous succinate with formulae CoxZn(1-x)Fe2(C4H4O4)3.6N2H4 (x = 0.0, 0.5, 1.0) were characterized by IR, CHNS, ICP-AES analysis, and their thermal studies were carried out by TG-DTA, TG-DTG, and isothermal mass loss studies. The ‘as prepared’ Co–Zn ferrites obtained by auto-catalytic thermal decomposition of precursors, on initial ignition, were characterized by XRD, IR, EDAX, TEM, and SEM. The SAED and XRD studies confirmed the formation of crystalline single phase nano Co–Zn ferrites. The morphology of these ‘as prepared’ ferrites was studies by TEM analysis which confirmed the particles to be in the nanometer range (20–30 nm). The increase in cobalt concentration resulted in reduced lattice parameter. The electrical resistivity declined while the Curie temperature surged with a decreased zinc concentration in ‘as prepared’ Co–Zn ferrites. The magnetization studies with the applied field at 300 K and 50 K displayed a gradual increase in magnetization values with the rise in cobalt content while confirming the super-paramagnetic nature of Co–Zn ferrite nano-system.

Anchoring Ligand-Effect on Bright Contrast-Enhancing Property of Hollow Mn3O4 Nanoparticle in T1-Weighted Magnetic Resonance Imaging

Here, we describe and conceptualize the influence of surface engineering for hollow manganese oxide nanoparticles (HMONs)-based contrast agents for magnetic resonance imaging (MRI). A systematic study has been conducted for enhancing the relaxivities of HMONs by functionalizing their surface with various capping ligands having different anchoring groups (carboxylate, alcohol, thiol, and amine). Among all studied ligands, carboxylate-anchored ligands exhibit significant increase in magnetization value upon surface capping of HMON. Contrary to the previous hypotheses based on the surface-Mn2+ ions accessibility to water molecules, we proposed surface capping induced magnetization in HMON is responsible for the enhanced relaxivity (r1) value. Further, in vivo imaging efficacy of oleate-capped HMON (OA-HMON) has been demonstrated in mouse brain. This study provides an insightful understanding of contrast enhancement and modulation by surface ligands on manganese oxide-based T1-contrast agents.

Chemical synthesis of Co/Cu core/shell nanocomposites and evaluation of their magnetic properties

Abstract Co/Cu core/shell nanocomposites (CSNCs) with varying shell thickness were synthesized through a modified polyol process in conjunction with a transmetallation reaction. Tuning of shell thickness was achieved by subtle change in concentration of copper acetate infused in different experiments against a fixed cobalt precursor concentration. Formation of Cu nanoparticles (NPs) was observed from UV–vis spectra, which showed a typical surface plasmon resonance peak at 560 nm. Precise control over particle size was obtained by the use of PVP as stabilizer, which was confirmed by a red shift of 20 cm −1 in the C O stretching frequency of various PVP coated Co/Cu CSNCs. Powder X-ray diffraction patterns elucidate the co-existence of distinctive fundamental peaks for both Co and Cu indicating that they have not formed an alloy during the reaction. TEM images corroborate with the above result by revealing the existence of lighter shaded Cu shells coated over dark inner cores of Co. Coalescence of adjacent Cu shells gives a matrix like appearance in case of Co 21.2 Cu 78.8 NPs; whereas Co 90.7 Cu 9.3 NPs were distinctly separated from each other. Magnetic hysteresis loops of all the Co/Cu CSNCs showed ferromagnetic behavior and an increase in magnetization value with decrease in shell thickness was observed.