Synthesis and Magnetic Behavior of Nickel Zinc Ferrite Nanoparticles Coated Onto Carbon Microcoils

ABSTRACTEpitaxial nickel zinc ferrite (Ni,Zn)Fe2O4 (NZF) thin films were successfully deposited on (MgO-Al2O3)/CeO2/YSZ/Si(001) substrates, where (MgO-Al2O3) is MgO doped with Al2O3. The crystallographic orientation and magnetic properties (saturation magnetization: Ms, and squareness: Mr/Ms where Mr is remanent magnetization) of NZF thin films were considerably changed with the amount of Al2O3 addition. If the amount of Al2O3 addition was less than 7 mol%, (001)-oriented epitaxial NZF thin films were obtained and the films had low squareness (around 45%). If the amount of Al2O3 addition was more than 7 mol%, (111)-oriented epitaxial NZF thin films were obtained and the films had high squareness (around 60–81%). Maximum squareness (81%) was obtained if the amount of Al2O3 addition was 26 mol%. For the sample with this Al2O3 content, the lattice mismatch between NZF and (MgO-Al2O3) buffer layer was 3.2%. The fact that high squareness was not obtained if lattice mismatch was very small (-0.3% on MgO) but obtained if lattice mismatch was 3.2% suggests that lattice mismatch to a certain content is important to avoid the formation of antiphase boundaries (APBs). This consideration was confirmed by examining other buffer layers having various lattice mismatches with NZF.

Download Full-text

Enhanced Transport Critical Current Density of Tl-1212 Bulk Superconductor Added with Nickel-Zinc Ferrite Nanoparticles

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.317.125 ◽

2021 ◽

Vol 317 ◽

pp. 125-130

Author(s):

Wei Kong ◽

Nurul Auni Khalid ◽

Wani Nadhirah Titingan Nizam ◽

Kim Yeow Tshai ◽

Ing Kong ◽

...

Keyword(s):

Critical Temperature ◽

Critical Current Density ◽

Critical Current ◽

Current Density ◽

Zinc Ferrite ◽

Density Measurement ◽

Ferrite Nanoparticles ◽

Transport Critical Current Density ◽

X Ray ◽

Nickel Zinc

High temperature superconductor Tl-1212 with nominal starting composition (Tl0.85Cr0.15)Sr2CaCu2O7-δ was prepared with high purity oxide powders using a solid state reaction method. Small amounts of nickel-zinc ferrite nanoparticles (Ni0.5Zn0.5Fe2O4) at compositions 0.01, 0.02, 0.05 and 0.10 wt. % were added into Tl-1212 superconductors. The effect of Ni0.5Zn0.5Fe2O4 nanoparticles’ addition on the critical temperature (Tc), transport critical current density (Jc), phase formation, and morphology was studied. The samples were characterized using electrical resistance measurement, transport critical current density measurement, powder X-ray diffraction method (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Zero-resistance critical temperature (Tc-zero) was found to rise from 97 K to 99 K with increasing Ni0.5Zn0.5Fe2O4 nanoparticles concentration. The highest value recorded for transport critical current density (Jc) was 3,120 mA/cm2 at 77 K, which exhibited by sample with 0.02 wt. % of Ni0.5Zn0.5Fe2O4 nanoparticles. All samples showed a dominant Tl-1212 phase and exhibited tetragonal lattice structure in the P4/mmm space group. SEM micrographs showed close-packed microstructure with low porosity. EDX mapping showed that Ni0.5Zn0.5Fe2O4 nanoparticles were well distributed in the Tl-1212 samples. This study demonstrated that Ni0.5Zn0.5Fe2O4 nanoparticles have functioned as effective flux pinning centers to Tl-1212 superconductors and thus significantly enhanced its Jc.

Download Full-text