期刊
PHYSICA B-CONDENSED MATTER
卷 403, 期 19-20, 页码 3760-3764出版社
ELSEVIER
DOI: 10.1016/j.physb.2008.07.002
关键词
Nanostructured materials; Magnetization; Mn3O4; Superparamagnetism; Chemical synthesis
资金
- Fatih University Research Project Foundation [P50020602]
- Knut and Alice Wallenbergs Foundation [UAW2004.0224]
Manganese oxide (Mn3O4) nanoparticles were successfully prepared by a novel oxidation-precipitation method based on oxidation of manganese sulfate to manganese salts and hydrolyzing with NaOH and concentrated NH3. X-ray diffraction (XRD) analysis confirmed the tetragonal haussmanite structure with average crystallite size of similar to 14 and similar to 11 nm: transmission electron microscopy (TEM) analysis showed crystallite size of 14 5 and 12 3 nm for NaOH- and NH3-hydrolyzed samples, respectively. The ferromagnetic transition temperatures are 38 and 40 K for NaOH- and NH3-hydrolyzed samples, respectively. These values are lower than that of bulk Mn3O4. Both samples show superparamagnetic behavior at room temperature, with no apparent saturation magnetization and hysteresis in the region of measured field strength, and they also exhibit relatively large coercivity below the ferromagnetic transition temperature. Below the transition, marked differences are observed in temperature dependence of magnetization, hysteresis loop shape, and type of the samples from the bulk values. The particles are considered as single magnetic domains with random orientations of magnetic moments and thermal fluctuations of anisotropic axes. These results are attributed to the smaller size (increase in surface to volume ratio) of the samples, which cause an increase of effective magnetic surface anisotropy. (C) 2008 Elsevier B.V. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据