Title:
Magnetic properties of bulk Zn₁₋ₓMnₓO and Zn₁₋ₓCoₓO single crystals
Magnetic properties of bulk Zn₁₋ₓMnₓO and Zn₁₋ₓCoₓO single crystals
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Kane, Matthew Hartmann
Shalini, K.
Summers, C. J.
Varatharajan, R.
Nause, J.
Vestal, Christy Riann
Zhang, Z. John
Ferguson, Ian T.
Shalini, K.
Summers, C. J.
Varatharajan, R.
Nause, J.
Vestal, Christy Riann
Zhang, Z. John
Ferguson, Ian T.
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Abstract
Manganese and cobalt-doped ZnO have been produced using a modified melt-growth technique. X-ray diffraction measurements indicate that the samples are high-quality single crystals with ω−2θ full width at half maximum values of 78 arc sec for the undoped ZnO and 252 arc sec for Zn₁₋ₓMnₓO (x = 0.05). The lattice parameter of the Zn₁₋ₓMnₓO was observed to increase with Mn concentration. Transmission measurements showed systematic variations dominated by absorption from interatomic Mn²⁺ and Co²⁺ transitions. No evidence of diluted magnetic semiconductor mean-field ferromagnetic behavior was observed in any of these nominally noncarrier-doped samples. The magnetic properties instead showed paramagnetic behavior for Zn₁₋ₓMnₓO dominated by an antiferromagnetic Mn–Mn exchange interaction at low temperatures. Zn ₁₋ₓ CoₓO showed hysteresis that was attributed to superparamagnetic Co clusters embedded in a diamagnetic ZnO matrix. It has been shown that in the bulk single-crystal form, intrinsic and noncarrier-doped Zn₁₋ₓTMₓO is not ferromagnetic; thus creative processing and doping techniques are necessary to achieve practical ferromagnetism in these materials.
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2004-12
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