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水热合成单晶La _1-x Ca _x MnO₃系列纳米线

晋传贵 , 张涛 , 李晓光

无机材料学报 doi:10.3724/SP.J.1077.2007.00243

采用水热法, 成功地合成了一系列单晶La _1-x Ca _x MnO₃(x=0.3、0.5、0.75)纳米线. X射线衍射(XRD)的结果表明所制备的样品是纯的La _1-x Ca _x MnO₃ 正交相(x=0.3、0.5、0.75)纳米线. 透射电子显微镜(TEM)的照片清晰地显示所制备的样品是由大量直径均匀(约90nm)、长度从几微米至几十微米的La _1-x Ca _x MnO₃的单晶纳米线构成. La _0.5 Ca _0.5 MnO ₃纳米线清晰的高分辨电子显微镜(HRTEM)的图片表明纳米线的表面是光滑的, 没有任何缺陷且La _0.5 Ca _0.5 MnO₃纳米线沿<100>方向生长. La _0.5 Ca _0.5 MnO ₃ 纳米线磁测量的结果表明相对于块材来说纳米线的Tc有明显地提高, 这是由于晶胞收缩和形状各向异性所致.

关键词: 水热法 , La1-xCaxMnO3 , nanowires , magnetic measurement

STRUCTURAL TRANSFORMATION INDUCED BY MECHANICALLY DRIVEN ALLOYING AND SUBSEQUENT MAGNETIC PROPERLIES OF THE Fe-Cu SYSTEM

Y.Z. Yang , Y.H Luo , Q.S. Li , Y.L. Zhu , X.M. Ma , Y.D. Dong and Y.Z. Chuang(Department of Materials Science and Engineering , Guangdong University of Technology , Guangzhou510090 , China)(Guangdong Educational College , Guangzhou 510084 , China)(Department of Materials Science and Engineering , Shanghai University , Shanghai 200072 , China)(Institute of Metal Research , The Chinese Academy of Sciences , Shenyang 110015 , China)

金属学报(英文版)

The structural transformation in Fe-Cu powder induced by mechanically driven alloying has been monitored by the lattice constant measurements and Mossbauer spectroscopy. For the samples with Cu higher than 75at.% Mossbauer the spectra show a broad paramagnetic doublet; for samples with 50 and 60at.%Cu a new broad ferromagnetic sextet; for those with less than 30at.%Cu similar to those of α-Fe. The main peaks of the hyperfine field distribution significantly broaden and shift to a lower position with increasing Cu content due to the complex environments of iron atoms in the solid solutions and the reduction in the nearest neighbor Fe of a cental Fe atom, respectively. The saturation magnetization of Fe-Cu alloys monotonously decreases with Cu content. The complex composition dependence of coercive field for the milled samples is discussed with respect to the solid dissolution, grain size, interfacial state etc.. The increase of lattice constants with the solute content in the two terminal solid solutions has been explained by the volume-size factor theory or magnetovolume effect.

关键词: mechanical alloying , null , null , null

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