CIN2(ICN-CSIC) and Universitat Autònoma de Barcelona, Catalan Institute of Nanotechnology, Campus de la UAB, 08193 Bellaterra (Barcelona), Spain.
Nanoscale. 2012 Aug 21;4(16):5138-47. doi: 10.1039/c2nr30986f. Epub 2012 Jul 13.
Inverted soft/hard, in contrast to conventional hard/soft, bi-magnetic core/shell nanoparticles of Mn(x)Fe(3-x)O(4)/Fe(x)Mn(3-x)O(4) with two different core sizes (7.5 and 11.5 nm) and fixed shell thickness (∼0.6 nm) have been synthesized. The structural characterization suggests that the particles have an interface with a graded composition. The magnetic characterization confirms the inverted soft/hard structure and evidences a strong exchange coupling between the core and the shell. Moreover, larger soft core sizes exhibit smaller coercivities and loop shifts, but larger blocking temperatures, as expected from spring-magnet or graded anisotropy structures. The results indicate that, similar to thin film systems, the magnetic properties of soft/hard core/shell nanoparticles can be fine tuned to match specific applications.
与传统的硬/软相反，我们合成了具有两种不同核尺寸（7.5nm 和 11.5nm）和固定壳厚度（约 0.6nm）的 Mn(x)Fe(3-x)O(4)/Fe(x)Mn(3-x)O(4)双磁芯/壳反铁磁/亚铁磁纳米粒子。结构特征表明这些粒子具有界面和分级组成。磁性特征证实了反铁磁/亚铁磁结构，并证明了核与壳之间存在强烈的交换耦合。此外，较大的软核尺寸表现出较小的矫顽力和磁滞回线移动，但较大的阻塞温度，这与弹簧磁体或梯度各向异性结构一致。结果表明，与薄膜系统类似，软/硬芯/壳纳米粒子的磁性可以进行精细调整以匹配特定的应用。
