Centro Atómico Bariloche, CNEA-CONICET, Av. Bustillo 9500, Bariloche, Río Negro, Argentina.
Nanoscale. 2017 Jul 27;9(29):10240-10247. doi: 10.1039/c7nr03740f.
In order to explore an alternative strategy to design exchange-biased magnetic nanostructures, bimagnetic core/shell nanoparticles have been fabricated by a thermal decomposition method and systematically studied as a function of the interface exchange coupling. The nanoparticles are constituted by a ∼3 nm antiferromagnetic (AFM) CoO core encapsulated in a ∼4 nm-thick CoZnFeO (x = 0-1) ferrimagnetic (FiM) shell. The system presents an enhancement of the coercivity (H) as compared to its FiM single-phase counterpart and exchange bias fields (H). While H decreases monotonically with the Zn concentration from ∼21.5 kOe for x = 0, to ∼7.1 kOe for x = 1, H exhibits a non-monotonous behavior being maximum, H ∼ 1.4 kOe, for intermediate concentrations. We found that the relationship between the AFM anisotropy energy and the exchange coupling energy can be tuned by replacing Co with Zn ions in the shell. As a consequence, the magnetization reversal mechanism of the system is changed from an AFM/FiM rigid-coupling regime to an exchange-biased regime, providing a new approach to tune the magnetic properties and to design novel hybrid nanostructures.
为了探索设计交换偏置磁纳米结构的替代策略，我们通过热分解法制备了双磁芯/壳纳米粒子，并系统地研究了它们作为界面交换耦合函数的性质。这些纳米粒子由约 3nm 的反铁磁（AFM）CoO 核和约 4nm 厚的 CoZnFeO（x=0-1）亚铁磁（FiM）壳组成。与单相 FiM 相比，该体系的矫顽力（H）和交换偏置场（H）得到了增强。虽然 H 随 Zn 浓度从 x=0 时的约 21.5kOe 单调减小到 x=1 时的约 7.1kOe，但 H 表现出非单调行为，在中间浓度时最大，H∼1.4kOe。我们发现，通过在壳中用 Zn 离子取代 Co，AFM 各向异性能与交换耦合能之间的关系可以得到调节。因此，该体系的磁化反转机制从 AFM/FiM 刚性耦合转变为交换偏置，为调节磁性能和设计新型混合纳米结构提供了一种新方法。
