Omelianchik A, Singh G, McDonagh Brigitte H, Rodionova V, Fiorani D, Peddis D, Laureti S
Center for Functionalized Magnetic Materials (FunMagMa), Immanuel Kant Baltic Federal University, 236041, Kaliningrad, Russia. Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM-CNR), nM2-lab, Via Salaria km 29300, Monterotondo Scalo, I-00015 Rome, Italy.
Nanotechnology. 2018 Feb 2;29(5):055703. doi: 10.1088/1361-6528/aa9e59.
Manganese oxide nanoparticles (MNOPs), when dispersed in a water solution, show a magnetic behavior that drastically changes after an aging process. In this paper, the variation in the magnetic properties has been correlated with the structural evolution of the nanoparticles: in particular, the as prepared MnO/MnO core/shell system manifests a low temperature magnetization reversal that is strongly affected by the presence of the MnO shell and, in particular, by the existence of a frustrated interfacial region playing a key role in determining the low temperature irreversibility, the finite coercivity slightly above the Curie temperature of the MnO phase and the horizontal displacement of the FC-hysteresis loop. On the other hand, the magnetic behavior of the aged system results dominated by the presence of MnO whose highly anisotropic character (i.e. high coercivity and high magnetization remanence) is attributed to the presence of a large fraction of surface spins. Such a result is consistent with the structural evolution, from core/shell to hollow nanoparticles, as shown by TEM observation.
氧化锰纳米颗粒（MNOPs）分散在水溶液中时，会表现出一种磁性行为，而这种行为在老化过程后会发生显著变化。在本文中，磁性特性的变化已与纳米颗粒的结构演变相关联：特别是，所制备的MnO/MnO核壳系统表现出低温磁化反转，这种反转受到MnO壳层的强烈影响，尤其是受到一个受挫界面区域的存在的强烈影响，该区域在决定低温不可逆性、略高于MnO相居里温度的有限矫顽力以及FC磁滞回线的水平位移方面起着关键作用。另一方面，老化系统的磁性行为主要由MnO的存在主导，其高度各向异性的特性（即高矫顽力和高剩磁）归因于大量表面自旋的存在。这一结果与从核壳纳米颗粒到空心纳米颗粒的结构演变一致，如透射电子显微镜（TEM）观察所示。
