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Title: Structural and ambient/sub-ambient temperature magnetic properties of Er-substituted cobalt-ferrites synthesized by sol-gel assisted auto-combustion method

Abstract

Er-substituted cobalt-ferrites CoFe{sub 2−x}Er{sub x}O{sub 4} (0 ≤ x ≤ 0.04) were synthesized by sol-gel assisted auto-combustion method. The precursor powders were calcined at 673–873 K for 4 h, subsequently pressed into pellets and sintered at 1273 K for 4 h. X-ray diffraction (XRD) confirmed the presence of the spinel phase for all the compositions and, additional orthoferrite phase for higher compositions (x = 0.03 and 0.04). The XRD spectra and the Transmission Electron Microscopy micrographs indicate that the nanocrystalline particulates of the Er-substituted cobalt ferrites have crystallite size of ∼120–200 nm. The magnetization curves show an increase in saturation magnetization (M{sub S}) and coercivity (H{sub C}) for Er-substituted cobalt-ferrites at sub-ambient temperatures. M{sub S} for CoFe{sub 2}O{sub 4}, CoFe{sub 0.99}Er{sub 0.01}O{sub 4}, CoFe{sub 0.98}Er{sub 0.02}O{sub 4}, and CoFe{sub 0.97}Er{sub 0.03}O{sub 4} peak at 89.7 Am{sup 2}/kg, 89.3 Am{sup 2}/kg, 88.8 Am{sup 2}/kg, and 87.1 Am{sup 2}/kg, respectively, at a sub-ambient temperature of ∼150 K. H{sub C} substantially increases with decrease in temperature for all the compositions, while it peaks at x = 0.01−0.02 at all temperatures. The combination of Er content—x ∼ 0.02 and the temperature—∼5 K provides the maximum H{sub C} ∼ 984 kA/m. Er-substituted cobalt-ferrites have higher cubic anisotropy constant, K{sub 1}, compared to pure cobalt-ferrite at ambient/sub-ambient temperatures. K{sub 1} gradually increases for all compositions in the temperature decreasing frommore » 300 to 100 K. While K{sub 1} peaks at ∼150 K for pure cobalt-ferrite, it peaks at ∼50 K for CoFe{sub 0.99}Er{sub 0.01}O{sub 4}, CoFe{sub 0.98}Er{sub 0.02}O{sub 4}, and CoFe{sub 0.96}Er{sub 0.04}O{sub 4}. The M{sub S} (∼88.7 Am{sup 2}/kg), at 5 K, for Er substituted cobalt-ferrite is close to the highest values reported for Sm and Gd substituted cobalt-ferrites. The M{sub S} (∼83.5 Am{sup 2}/kg) at 300 K for Er-substituted cobalt-ferrite is the highest among the lanthanide series element substituted cobalt-ferrites. The H{sub C} (at 5 K) for Er substituted cobalt-ferrite is close to the highest values observed for La, Ce, Nd, Sm, and Gd substituted cobalt-ferrites.« less

Authors:
 [1];  [2];  [1]
  1. School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046 (India)
  2. Department of Metallurgical Engineering and Materials Science, IIT-Bombay, Mumbai 400076 (India)
Publication Date:
OSTI Identifier:
22308730
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 116; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; AMBIENT TEMPERATURE; ANISOTROPY; COBALT COMPOUNDS; COBALT OXIDES; COERCIVE FORCE; CRYSTALS; ERBIUM ADDITIONS; ERBIUM OXIDES; FERRITES; MAGNETIC PROPERTIES; MAGNETIZATION; NANOSTRUCTURES; POWDERS; RARE EARTHS; SATURATION; SOL-GEL PROCESS; SPECTRA; SPINELS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION

Citation Formats

Prathapani, Sateesh, Department of Metallurgical Engineering and Materials Science, IIT-Bombay, Mumbai 400076, Jayaraman, Tanjore V., E-mail: ddas@uohyd.ernet.in, E-mail: tvjayaraman@gmail.com, Varaprasadarao, Eswara K., and Das, Dibakar. Structural and ambient/sub-ambient temperature magnetic properties of Er-substituted cobalt-ferrites synthesized by sol-gel assisted auto-combustion method. United States: N. p., 2014. Web. doi:10.1063/1.4889929.
Prathapani, Sateesh, Department of Metallurgical Engineering and Materials Science, IIT-Bombay, Mumbai 400076, Jayaraman, Tanjore V., E-mail: ddas@uohyd.ernet.in, E-mail: tvjayaraman@gmail.com, Varaprasadarao, Eswara K., & Das, Dibakar. Structural and ambient/sub-ambient temperature magnetic properties of Er-substituted cobalt-ferrites synthesized by sol-gel assisted auto-combustion method. United States. doi:10.1063/1.4889929.
Prathapani, Sateesh, Department of Metallurgical Engineering and Materials Science, IIT-Bombay, Mumbai 400076, Jayaraman, Tanjore V., E-mail: ddas@uohyd.ernet.in, E-mail: tvjayaraman@gmail.com, Varaprasadarao, Eswara K., and Das, Dibakar. Mon . "Structural and ambient/sub-ambient temperature magnetic properties of Er-substituted cobalt-ferrites synthesized by sol-gel assisted auto-combustion method". United States. doi:10.1063/1.4889929.
@article{osti_22308730,
title = {Structural and ambient/sub-ambient temperature magnetic properties of Er-substituted cobalt-ferrites synthesized by sol-gel assisted auto-combustion method},
author = {Prathapani, Sateesh and Department of Metallurgical Engineering and Materials Science, IIT-Bombay, Mumbai 400076 and Jayaraman, Tanjore V., E-mail: ddas@uohyd.ernet.in, E-mail: tvjayaraman@gmail.com and Varaprasadarao, Eswara K. and Das, Dibakar},
abstractNote = {Er-substituted cobalt-ferrites CoFe{sub 2−x}Er{sub x}O{sub 4} (0 ≤ x ≤ 0.04) were synthesized by sol-gel assisted auto-combustion method. The precursor powders were calcined at 673–873 K for 4 h, subsequently pressed into pellets and sintered at 1273 K for 4 h. X-ray diffraction (XRD) confirmed the presence of the spinel phase for all the compositions and, additional orthoferrite phase for higher compositions (x = 0.03 and 0.04). The XRD spectra and the Transmission Electron Microscopy micrographs indicate that the nanocrystalline particulates of the Er-substituted cobalt ferrites have crystallite size of ∼120–200 nm. The magnetization curves show an increase in saturation magnetization (M{sub S}) and coercivity (H{sub C}) for Er-substituted cobalt-ferrites at sub-ambient temperatures. M{sub S} for CoFe{sub 2}O{sub 4}, CoFe{sub 0.99}Er{sub 0.01}O{sub 4}, CoFe{sub 0.98}Er{sub 0.02}O{sub 4}, and CoFe{sub 0.97}Er{sub 0.03}O{sub 4} peak at 89.7 Am{sup 2}/kg, 89.3 Am{sup 2}/kg, 88.8 Am{sup 2}/kg, and 87.1 Am{sup 2}/kg, respectively, at a sub-ambient temperature of ∼150 K. H{sub C} substantially increases with decrease in temperature for all the compositions, while it peaks at x = 0.01−0.02 at all temperatures. The combination of Er content—x ∼ 0.02 and the temperature—∼5 K provides the maximum H{sub C} ∼ 984 kA/m. Er-substituted cobalt-ferrites have higher cubic anisotropy constant, K{sub 1}, compared to pure cobalt-ferrite at ambient/sub-ambient temperatures. K{sub 1} gradually increases for all compositions in the temperature decreasing from 300 to 100 K. While K{sub 1} peaks at ∼150 K for pure cobalt-ferrite, it peaks at ∼50 K for CoFe{sub 0.99}Er{sub 0.01}O{sub 4}, CoFe{sub 0.98}Er{sub 0.02}O{sub 4}, and CoFe{sub 0.96}Er{sub 0.04}O{sub 4}. The M{sub S} (∼88.7 Am{sup 2}/kg), at 5 K, for Er substituted cobalt-ferrite is close to the highest values reported for Sm and Gd substituted cobalt-ferrites. The M{sub S} (∼83.5 Am{sup 2}/kg) at 300 K for Er-substituted cobalt-ferrite is the highest among the lanthanide series element substituted cobalt-ferrites. The H{sub C} (at 5 K) for Er substituted cobalt-ferrite is close to the highest values observed for La, Ce, Nd, Sm, and Gd substituted cobalt-ferrites.},
doi = {10.1063/1.4889929},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 2,
volume = 116,
place = {United States},
year = {2014},
month = {7}
}