Magnetism in Mn-doped ZnO nanoparticles prepared by a co-precipitation method
Magnetism in Mn-doped ZnO nanoparticles prepared by a co-precipitation method
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DOI：
10.1088/0957-4484/17/5/020
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发表时间：
2006-03-14
期刊：
影响因子：
3.5
通讯作者：
Kulshreshtha, SK
中科院分区：
文献类型：
--
作者：
Jayakumar, OD;Salunke, HG;Kulshreshtha, SK
我们报道了通过共沉淀法合成标称 2 和 5 at.% Mn 掺杂 ZnO 纳米晶颗粒。 Rietveld 对 X 射线衍射数据的精修表明，Mn 掺杂的 ZnO 以单相纤锌矿结构结晶，并且晶胞体积随着 Mn 浓度的增加而增加。 DC 磁化测量表明，在 675 K 退火的标称 2 at.% Mn 掺杂 ZnO 纳米粒子在高于室温时，H-c 类似于 150 Oe。在 675 K 退火的 2 at.% Mn 掺杂 ZnO 纳米粒子的 EPR 光谱中观察到明显的铁磁共振 (FMR) 信号。 用于估计参与铁磁排序的自旋数量。在 2 at.% Mn ZnO 晶格中存在的总 Mn 中，25% 的 Mn2+ 离子负责铁磁有序，而近 5% 的 Mn2+ 离子保持未耦合（孤立自旋）。在 875-1275 K 退火的 5% Mn 掺杂 ZnO 样品（g = 2.007，A = 80 G，D = 2·10 G 和 E = 15 G）的高分辨率 EPR 光谱证实，Mn 以 Mn 的形式替代并入 ZnO 晶格中。当退火温度超过 1075 K 时，2 at.% 和 5 at.% Mn 掺杂 ZnO 样品中都会出现杂质相，该杂质相已被鉴定为 (Zn1-XMn(II)(X))Mn(III)(2)O-4 的变体，T-C 类似于 15 K。我们的结果表明，在 Mn 掺杂 ZnO 中观察到的室温铁磁性可归因于 Mn 在 Zn 位点的取代结合，而不是由于任何亚稳态第二相的形成。
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 H-c similar to 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 = 2 10 G and E = 15 G) confirmed that Mn was substitutionally incorporated into the ZnO lattice as Mn. 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)(2)O-4 with T-C similar to 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.