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Magnetism in Mn-doped ZnO nanoparticles prepared by a co-precipitation method

Jayakumar, O D and Salunke, H G and Kadam, R M and Mohapatra, Manoj and Yaswant, G and Kulshreshtha, S K (2006) Magnetism in Mn-doped ZnO nanoparticles prepared by a co-precipitation method. Nanotechnology, 17 (5). pp. 1278-1285.

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Official URL: http://stacks.iop.org/0957-4484/17/1278

Abstract

We report the synthesis of nominal 2 and 5 at.% Mn-doped ZnO nanocrystalline particles by a co-precipitation method. Rietveld refinement of x-ray diffraction data revealed that Mn-doped ZnO crystallizes in the monophasic wurtzite structure and the unit cell volume increases with increasing Mn concentration. DC magnetization measurements showed ferromagnetic ordering above room temperature with Hc ∼ 150 Oe for nominal 2 at.% Mn-doped ZnO nanoparticles annealed at 675 K. A distinct ferromagnetic resonance (FMR) signal was observed in the EPR spectra of the 2 at.% Mn-doped ZnO nanoparticles annealed at 675 K. EPR measurements were used to estimate the number of spins participating in ferromagnetic ordering. Of the total Mn present in the 2 at.% Mn ZnO lattice, 25% of the Mn2+ ions were responsible for ferromagnetic ordering, whereas nearly 5% of the Mn2+ ions remained uncoupled (isolated spins). A well resolved EPR spectrum of 5% Mn-doped ZnO samples annealed at 875–1275 K (g = 2.007, A = 80 G, D = 210 G and E = 15 G) confirmed that Mn was substitutionally incorporated into the ZnO lattice as Mn2+. On increasing the temperature of annealing beyond 1075 K an impurity phase emerges in both the 2 and 5 at.% Mn-doped ZnO samples, which has been identified as a variant of (Zn1−XMn(II)X )Mn(III)2O4 with Tc ∼ 15 K. Our results indicate that the observed room temperature ferromagnetism in Mn-doped ZnO can be attributed to the substitutional incorporation of Mn at Zn-sites rather than due to the formation of any metastable secondary phases.

Item Type:Article
Subjects:Physical Science > Nanophysics
Physical Science > Nanomagnetics
ID Code:355
Deposited By:Lesley Tobin
Deposited On:01 Dec 2008 15:56
Last Modified:09 Feb 2009 16:51

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