Centre d'Investigació en Nanociència i Nanotecnologia (ICN-CSIC), Campus Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
J Am Chem Soc. 2010 Jul 14;132(27):9398-407. doi: 10.1021/ja1021798.
The magnetic properties of bimagnetic core/shell nanoparticles consisting of an antiferromagnetic MnO core and a ferrimagnetic passivation shell have been investigated. It is found that the phase of the passivation shell (gamma-Mn(2)O(3) or Mn(3)O(4)) depends on the size of the nanoparticles. Structural and magnetic characterizations concur that while the smallest nanoparticles have a predominantly gamma-Mn(2)O(3) shell, larger ones have increasing amounts of Mn(3)O(4). A considerable enhancement of the Néel temperature, T(N), and the magnetic anisotropy of the MnO core for decreasing core sizes has been observed. The size reduction also leads to other phenomena such as persistent magnetic moment in MnO up to high temperatures and an unusual temperature behavior of the magnetic domains.
研究了由反铁磁 MnO 核和亚铁磁钝化壳组成的双磁核/壳纳米粒子的磁性。结果发现，钝化壳的相（γ-Mn(2)O(3)或 Mn(3)O(4))取决于纳米粒子的尺寸。结构和磁性特征表明，最小的纳米粒子主要具有γ-Mn(2)O(3)壳，而较大的纳米粒子则具有越来越多的 Mn(3)O(4)。随着核心尺寸的减小，观察到 MnO 的尼尔温度 T(N)和磁各向异性得到了相当大的提高。尺寸减小还导致了其他现象，例如 MnO 中高达高温的持久磁矩和磁畴的异常温度行为。
