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Title: Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite

Here, we report on the effect of molybdenum (Mo) incorporation on the crystal structure, surface morphology, Mo chemical valence state, and magnetic properties of cobalt ferrite (CoFe 2O 4, referred to CFO). Molybdenum incorporated cobalt ferrite (CoFe 2–xMo xO 4, referred to CFMO) ceramics were prepared by the conventional solid-state reaction method by varying the Mo concentration in the range of x = 0.0–0.3. X-ray diffraction studies indicate that the CFMO materials crystallize in inverse spinel cubic phase. Molybdenum incorporation induced lattice parameter increase from 8.322 to 8.343 Å coupled with a significant increase in density from 5.4 to 5.7 g/cm 3 was evident in structural analyses. Scanning electron microscopy imaging analyses indicate that the Mo incorporation induces agglomeration of particles leading to larger particle size with increasing x(Mo) values. Detailed X-ray photoelectron spectroscopic (XPS) analyses indicate the increasing Mo content with increasing x from 0.0 to 0.3. XPS confirms that the chemistry of Mo is complex in these CFMO compounds; Mo ions exist in the lower oxidation state (Mo 4+) for higher x while in a mixed chemical valence state (Mo 4+, Mo 5+, Mo 6+) for lower x values. From the temperature-dependent magnetization, the samples show ferrimagnetic behaviormore » including the pristine CFO. From the isothermal magnetization measurements, we find almost 2-fold decrease in coercive field ( H c) from 2143 to 1145 Oe with the increase in Mo doping up to 30%. This doping-dependent H c is consistently observed at all the temperatures measured (4, 100, 200, and 300 K). Furthermore, the saturation magnetization estimated at 4 K and at 1.5 T (from M–H loops) goes through a peak at 92 emu/g (at 15% Mo doping) from 81 emu/g (pristine CFO), and starts decreasing to 79 emu/g (at 30% Mo doping). The results demonstrate that the crystal structure, microstructure, and magnetic properties can be tuned by controlling the Mo-content in the CFMO materials.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [3] ;  [1]
  1. Univ. of Texas at El Paso, El Paso, TX (United States)
  2. Boise State Univ., Boise, ID (United States)
  3. Ames Lab., Ames, IA (United States)
Publication Date:
Report Number(s):
IS-J-9501
Journal ID: ISSN 1932-7447
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 121; Journal Issue: 45; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE
OSTI Identifier:
1410340

Orozco, C., Melendez, A., Manadhar, S., Singamaneni, S. R., Reddy, Kongara M., Gandha, K., Niebedim, I. C., and Ramana, C. V.. Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite. United States: N. p., Web. doi:10.1021/acs.jpcc.7b08162.
Orozco, C., Melendez, A., Manadhar, S., Singamaneni, S. R., Reddy, Kongara M., Gandha, K., Niebedim, I. C., & Ramana, C. V.. Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite. United States. doi:10.1021/acs.jpcc.7b08162.
Orozco, C., Melendez, A., Manadhar, S., Singamaneni, S. R., Reddy, Kongara M., Gandha, K., Niebedim, I. C., and Ramana, C. V.. 2017. "Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite". United States. doi:10.1021/acs.jpcc.7b08162. https://www.osti.gov/servlets/purl/1410340.
@article{osti_1410340,
title = {Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite},
author = {Orozco, C. and Melendez, A. and Manadhar, S. and Singamaneni, S. R. and Reddy, Kongara M. and Gandha, K. and Niebedim, I. C. and Ramana, C. V.},
abstractNote = {Here, we report on the effect of molybdenum (Mo) incorporation on the crystal structure, surface morphology, Mo chemical valence state, and magnetic properties of cobalt ferrite (CoFe2O4, referred to CFO). Molybdenum incorporated cobalt ferrite (CoFe2–xMoxO4, referred to CFMO) ceramics were prepared by the conventional solid-state reaction method by varying the Mo concentration in the range of x = 0.0–0.3. X-ray diffraction studies indicate that the CFMO materials crystallize in inverse spinel cubic phase. Molybdenum incorporation induced lattice parameter increase from 8.322 to 8.343 Å coupled with a significant increase in density from 5.4 to 5.7 g/cm3 was evident in structural analyses. Scanning electron microscopy imaging analyses indicate that the Mo incorporation induces agglomeration of particles leading to larger particle size with increasing x(Mo) values. Detailed X-ray photoelectron spectroscopic (XPS) analyses indicate the increasing Mo content with increasing x from 0.0 to 0.3. XPS confirms that the chemistry of Mo is complex in these CFMO compounds; Mo ions exist in the lower oxidation state (Mo4+) for higher x while in a mixed chemical valence state (Mo4+, Mo5+, Mo6+) for lower x values. From the temperature-dependent magnetization, the samples show ferrimagnetic behavior including the pristine CFO. From the isothermal magnetization measurements, we find almost 2-fold decrease in coercive field (Hc) from 2143 to 1145 Oe with the increase in Mo doping up to 30%. This doping-dependent Hc is consistently observed at all the temperatures measured (4, 100, 200, and 300 K). Furthermore, the saturation magnetization estimated at 4 K and at 1.5 T (from M–H loops) goes through a peak at 92 emu/g (at 15% Mo doping) from 81 emu/g (pristine CFO), and starts decreasing to 79 emu/g (at 30% Mo doping). The results demonstrate that the crystal structure, microstructure, and magnetic properties can be tuned by controlling the Mo-content in the CFMO materials.},
doi = {10.1021/acs.jpcc.7b08162},
journal = {Journal of Physical Chemistry. C},
number = 45,
volume = 121,
place = {United States},
year = {2017},
month = {9}
}