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Relationship between the structural and magnetic properties of Co-doped $Sn O_{2}$ nanoparticles

J. Hays, A. Punnoose, R. Baldner, M. H. Engelhard, J. Peloquin, and K. M. Reddy

Phys. Rev. B 72, 075203 – Published 5 August 2005

Abstract

In this paper, we present the results of a detailed investigation of the structural, optical, and magnetic properties of chemically synthesized pure and Co-doped $Sn O_{2}$ powders using x-ray diffraction (XRD), diffuse reflectance spectroscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, and magnetometry. In ${Sn}_{1 - x} {Co}_{x} O_{2}$ samples prepared at $600 ° C$ with low doping concentrations of Co $(⩽ 1 %)$ , the $Sn O_{2}$ lattice contracts, band gap energy decreases, and a ferromagnetic behavior is developed. Increasing the Co doping concentration to $> 1 %$ leads to a rapid expansion of the lattice and significant structural disorder evidenced by changes in the XRD and Raman spectra presumably due to additional interstitial incorporation of Co. This higher Co doping completely destroys the ferromagnetism. The striking similarity between the changes in the lattice parameters and the magnetic properties of ${Sn}_{1 - x} {Co}_{x} O_{2}$ indicates a structure-magnetic property relationship.

Received 2 September 2004

DOI:https://doi.org/10.1103/PhysRevB.72.075203

Authors & Affiliations

J. Hays and A. Punnoose^*

Department of Physics, Boise State University, Boise, Idaho 83725, USA

R. Baldner

Analytical Chemistry Lab, Micron Technology, Boise, Idaho 83707, USA

M. H. Engelhard

Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA

J. Peloquin

Department of Chemistry, Boise State University, Boise, Idaho 83725, USA

K. M. Reddy

Department of Physics, Boise State University, Boise, Idaho 83725, USA

^*Author to whom all correspondence should be addressed; Email address: [email protected]

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Vol. 72, Iss. 7 — 15 August 2005

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Figure 1
(a) Intensity of the tetragonal cassiterite peak (110) and the orthorhombic fraction $x_{o}$ of ${Sn}_{1 - x} {Co}_{x} O_{2}$ prepared at $600 ° C$ as a function of Co percentage. (b) The particle size of ${Sn}_{1 - x} {Co}_{x} O_{2}$ as a function of $x$ calculated from the XRD tetragonal cassiterite peak (110). The particle sizes determined from TEM are marked with stars. (c) Changes in the lattice parameters $a$ and $c$ of cassiterite $Sn O_{2}$ as a function of Co percentage. Stars indicate the bulk values of the $Sn O_{2}$ lattice parameters from XRD reference files. (d) Changes in the (110) cassiterite peak position with Co concentration. The lattice parameters were calculated using (110) and (202) peaks of the tetragonal cassiterite phase.Reuse & Permissions
Figure 2
Diffuse reflectance spectra of ${Sn}_{1 - x} {Co}_{x} O_{2}$ samples prepared at $600 ° C$ . (a) The changes in the absorption edge with Co concentration; inset in panel (a) shows the changes in the band gap energy estimated from the reflectance data as a function of Co concentration and (b) shows the complete spectra indicating the extent of ${Co}_{3} O_{4}$ formation.Reuse & Permissions
Figure 3
(a) Raman spectra of ${Sn}_{1 - x} {Co}_{x} O_{2}$ prepared at $600 ° C$ as a function of $x$ . (b) Raman spectra of pure $Sn O_{2}$ , 1% Co-doped $Sn O_{2}$ and a physical mixture of pure $Sn O_{2}$ and ${Co}_{3} O_{4}$ . (c) The apparent disappearance of $Sn O_{2}$ Raman peak at $630 {cm}^{- 1}$ and the emergence of the $617 {cm}^{- 1}$ peak of ${Co}_{3} O_{4}$ for $x > 0.01$ .Reuse & Permissions
Figure 4
(a) XPS spectra of ${Sn}_{1 - x} {Co}_{x} O_{2}$ prepared at $600 ° C$ as a function of Co percentage and (b) shows similar data of ${Co}_{3} O_{4}$ $(x = 1)$ and $Sn O_{2}$ $(x = 0)$ reference samples prepared under identical synthesis conditions.Reuse & Permissions
Figure 5
(a) and (b) The variation of the atomic percentages of Co, Sn, and O and the $Co ∕ Sn$ ratio as a function of Co concentration calculated using the corresponding XPS peak intensities.Reuse & Permissions
Figure 6
(a) The low field region of the room-temperature hysteresis loop of $600 ° C$ prepared ${Sn}_{0.99} {Co}_{0.01} O_{2}$ sample showing a coercivity of $9 Oe$ ; the inset in (a) shows the complete hysteresis loop of $600 ° C$ prepared ${Sn}_{0.99} {Co}_{0.01} O_{2}$ showing saturation of the sample magnetization expected for a ferromagnetic system, (b) variation of the room-temperature coercivity $H_{c}$ and remanence $M_{r}$ of ${Sn}_{1 - x} {Co}_{x} O_{2}$ prepared at $350 ° C$ as a function of $x$ ; inset in (b) shows the expanded view of the low-field region of the hysteresis loop of $350 ° C$ prepared ${Sn}_{0.995} {Co}_{0.005} O_{2}$ sample, and (c) variation of the saturation magnetization $M_{s}$ with $x$ of ${Sn}_{1 - x} {Co}_{x} O_{2}$ samples prepared at 350 (open circles) and $600 ° C$ (solid stars), and the lattice volume $V$ calculated using the $a$ and $c$ values of Fig. 1c (shown with solid squares) as a function of Co-doping concentration for the $600 ° C$ prepared ${Sn}_{1 - x} {Co}_{x} O_{2}$ .Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Relationship between the structural and magnetic properties of Co-doped $Sn O_{2}$ nanoparticles

J. Hays, A. Punnoose, R. Baldner, M. H. Engelhard, J. Peloquin, and K. M. Reddy

Phys. Rev. B 72, 075203 – Published 5 August 2005

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Physical Review B

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Relationship between the structural and magnetic properties of Co-doped SnO2 nanoparticles

J. Hays, A. Punnoose, R. Baldner, M. H. Engelhard, J. Peloquin, and K. M. Reddy

Phys. Rev. B 72, 075203 – Published 5 August 2005

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Relationship between the structural and magnetic properties of Co-doped $Sn O_{2}$ nanoparticles