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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}
}
  • The emergence of magnetic properties and quadratic magnetoelectric coupling in a material with outstanding ferroelectric properties has been pursued. Thus, the multiferroicity driven by the substitution of rare earth R{sup 3+} ions (R = Sm, Nd) on the A-site of PbTiO{sub 3} perovskite ceramics has been investigated. In some samples, a transition element with large ionic radius, like Fe{sup 2+}, has been also added on the A site. Polycrystalline ceramic samples with composition (Pb{sub 1-3x/2-y}R{sub x}Fe{sub y}) (Ti{sub 0.98}Mn{sub 0.02})O{sub 3} (R = Sm; x = 0.08, y = 0.035) and (Pb{sub 1−3x/2}R{sub x})(Ti{sub 0.98}Mn{sub 0.02})O{sub 3} (R = Nd, x = 0.08) have been prepared by conventional solid state ceramic processing,more » starting from reagent grade oxide powders. X-ray diffraction analysis confirmed the obtaining of a crystalline phase with tetragonal P4 mm symmetry. Transmission electron microscopy and high resolution transmission electron microscopy investigations have been carried out in order to analyze the local structure. Temperature dependence of dielectric permittivity revealed a strong anomaly at the temperature T{sub c} of the paraelectric-ferroelectric phase transition. Transition temperature values depend on the R ion type and are lower than in pure lead titanate by 80–100 K. A broad anomaly of dielectric permittivity is found below 140–180 K, where magnetization also increases due to the quadratic magnetoelectric coupling between ferroelectric and magnetic states. For the (Pb{sub 0.845}Sm{sub 0.08}Fe{sub 0.035})(Ti{sub 0.98}Mn{sub 0.02})O{sub 3} composition, the piezoelectric charge coefficient at room temperature was d{sub 31} ∼−6.5 pC/N and the remanent magnetization M{sub r} at room temperature was about 0.1 emu/g.« less
  • Metal to insulator transition was observed in Si{sub 0.02}Zn{sub 0.98}O (SZO) films, grown by pulsed laser deposition on sapphire substrates, as the thicknesses of the films were reduced from ∼40 to 15 nm. The SZO film with thickness of ∼40 nm showed typical metallic behavior in temperature dependent resistivity measurements. On the contrary, the SZO film with thickness of ∼15 nm was found to exhibit strong localization where the transport at low temperature was dominated by variable range hopping conduction. In the intermediate thickness regime, quantum corrections were important and a dimensional crossover from 3D to 2D weak localization occurred in the SZOmore » film with thickness of 20 nm.« less
  • Lattice dynamics and phase transition of MgO modified Pb{sub 0.99}(Zr{sub 0.95}Ti{sub 0.05}){sub 0.98}Nb{sub 0.02}O{sub 3} (PZTN-x wt. % MgO, x = 0, 0.1, 0.2, 0.5) ceramics have been investigated by far-infrared (FIR) reflectance in the temperature range of 5.5–300 K and Raman spectra between 77 and 300 K, respectively. With the aid of above complementary methods, the structure of all ceramics was defined as low-temperature ferroelectric rhombohedral phase [F{sub R(LT)}] at room temperature. The FIR dielectric functions were extracted from the multi-Lorentz oscillator dispersion model. The lowest frequency phonon mode, which is related to Pb-BO{sub 3} (B = Zr, Ti, Nb) vibration, mainly dominates the FIRmore » dielectric response. With increasing MgO composition, the dielectric constants ε(0) at room temperature are estimated to 85.4, 73.4, 73.9, and 41.9, respectively. The decreasing trend can be due to the doubly ionized oxygen vacancies induced by Mg substitution for B-site. The order-disorder phase transition located around 120 K can be clearly clarified from temperature evolution of phonon frequency, damping, and intensity. It decreases slightly with increasing MgO composition, which influence the distortion due to the broken correlation chains and local permanent dipoles creation. Moreover, the transformation from antiferroelectric orthorhombic A{sub O} to [ F{sub R(LT)} ] phase has been observed around 250 K, which is associated with the antiferroelectric displacement of Pb atoms along 〈 110 〉 and coupled rotations of the corner-connected oxygen octahedral. Furthermore, the transition from [ F{sub R(LT)} ] to [ F{sub R(HT)} ] (high-temperature ferroelectric rhombohedral phase) was identified around 290 K for MgO-doped PZTN ceramics. It arises from the shift of cation (Pb and Zr/Ti/Nb/Mg ions) along the 〈 111 〉 direction and the transition temperature slightly decreases compared to the pure ceramic.« less
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