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Title: Development and processing temperature dependence of ferromagnetism in Zn{sub 0.98}Co{sub 0.02}O

Abstract

We report the development of room-temperature ferromagnetism (FM), with coercivity H{sub c}=2000 Oe and saturation magnetization M{sub s}{approx}0.01 emu/g, in chemically synthesized powders of Zn{sub 0.98}Co{sub 0.02}O processed at 150 deg. C, and paramagnetism with antiferromagnetic interactions between the Co{sup 2+} spins (S=3/2) in samples processed at higher temperatures 200{<=}T{sub P}{<=}900 deg. C. X-ray diffraction data show a decrease in the lattice parameters a and c with T{sub P}, indicating a progressive incorporation of 0.58A sized tetrahedral Co{sup 2+} at the substitutional sites of 0.60 A sized Zn{sup 2+}. Diffuse reflectance spectra show three well defined absorption edges at 660, 615, and 568 nm due to the d-d crystal field transitions {sup 4}A{sub 2}(F){yields}{sup 2}E(G),{sup 4}A{sub 2}(F){yields}{sup 4}T{sub 1}(P), and {sup 4}A{sub 2}(F){yields}{sup 2}T{sub 1}(G) of high spin (S=3/2)Co{sup 2+} in a tetrahedral crystal field, whose intensities increase with processing temperature. X-ray photoelectron spectroscopy shows that the doped Co{sup 2+} ions in the 150 deg. C processed samples are located mostly on the surface of the particles and they disperse into the entire volume of the particles when processed at higher temperatures. The observations suggest that the FM most likely results from Co{sup 2+} attached to the surface sites andmore » it is lost in well dispersed samples formed at T{sub P}>150 deg. C.« less

Authors:
; ; ; ;  [1];  [2]
  1. Department of Physics, Boise State University, Boise, Idaho 83725-1570 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20788138
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 99; Journal Issue: 8; Conference: 50. annual conference on magnetism and magnetic materials, San Jose, CA (United States), 30 Oct - 3 Nov 2005; Other Information: DOI: 10.1063/1.2173956; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION; ANTIFERROMAGNETISM; COBALT IONS; COBALT OXIDES; COERCIVE FORCE; CRYSTAL FIELD; DOPED MATERIALS; FERROMAGNETISM; LATTICE PARAMETERS; MAGNETIZATION; PARAMAGNETISM; SPIN; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; TEMPERATURE RANGE 1000-4000 K; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY; ZINC COMPOUNDS; ZINC IONS

Citation Formats

Hays, J., Thurber, A., Reddy, K. M., Punnoose, A., Engelhard, M. H., and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352. Development and processing temperature dependence of ferromagnetism in Zn{sub 0.98}Co{sub 0.02}O. United States: N. p., 2006. Web. doi:10.1063/1.2173956.
Hays, J., Thurber, A., Reddy, K. M., Punnoose, A., Engelhard, M. H., & Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352. Development and processing temperature dependence of ferromagnetism in Zn{sub 0.98}Co{sub 0.02}O. United States. doi:10.1063/1.2173956.
Hays, J., Thurber, A., Reddy, K. M., Punnoose, A., Engelhard, M. H., and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352. Sat . "Development and processing temperature dependence of ferromagnetism in Zn{sub 0.98}Co{sub 0.02}O". United States. doi:10.1063/1.2173956.
@article{osti_20788138,
title = {Development and processing temperature dependence of ferromagnetism in Zn{sub 0.98}Co{sub 0.02}O},
author = {Hays, J. and Thurber, A. and Reddy, K. M. and Punnoose, A. and Engelhard, M. H. and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352},
abstractNote = {We report the development of room-temperature ferromagnetism (FM), with coercivity H{sub c}=2000 Oe and saturation magnetization M{sub s}{approx}0.01 emu/g, in chemically synthesized powders of Zn{sub 0.98}Co{sub 0.02}O processed at 150 deg. C, and paramagnetism with antiferromagnetic interactions between the Co{sup 2+} spins (S=3/2) in samples processed at higher temperatures 200{<=}T{sub P}{<=}900 deg. C. X-ray diffraction data show a decrease in the lattice parameters a and c with T{sub P}, indicating a progressive incorporation of 0.58A sized tetrahedral Co{sup 2+} at the substitutional sites of 0.60 A sized Zn{sup 2+}. Diffuse reflectance spectra show three well defined absorption edges at 660, 615, and 568 nm due to the d-d crystal field transitions {sup 4}A{sub 2}(F){yields}{sup 2}E(G),{sup 4}A{sub 2}(F){yields}{sup 4}T{sub 1}(P), and {sup 4}A{sub 2}(F){yields}{sup 2}T{sub 1}(G) of high spin (S=3/2)Co{sup 2+} in a tetrahedral crystal field, whose intensities increase with processing temperature. X-ray photoelectron spectroscopy shows that the doped Co{sup 2+} ions in the 150 deg. C processed samples are located mostly on the surface of the particles and they disperse into the entire volume of the particles when processed at higher temperatures. The observations suggest that the FM most likely results from Co{sup 2+} attached to the surface sites and it is lost in well dispersed samples formed at T{sub P}>150 deg. C.},
doi = {10.1063/1.2173956},
journal = {Journal of Applied Physics},
number = 8,
volume = 99,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}