1] ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, E-08193 Bellaterra, Barcelona, Spain [2] Departament de Química Inorgànica, Universitat de Barcelona, Diagonal 645, E-08028 Barcelona, Spain.
1] ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, E-08193 Bellaterra, Barcelona, Spain [2] INSTM and Dipartimento di Chimica 'U. Schiff', Università degli Studi di Firenze, Via della Lastruccia 3, Sesto Fiorentino, I-50019 Firenze, Italy.
Nat Commun. 2013;4:2960. doi: 10.1038/ncomms3960.
The growing miniaturization demand of magnetic devices is fuelling the recent interest in bi-magnetic nanoparticles as ultimate small components. One of the main goals has been to reproduce practical magnetic properties observed so far in layered systems. In this context, although useful effects such as exchange bias or spring magnets have been demonstrated in core/shell nanoparticles, other interesting key properties for devices remain elusive. Here we show a robust antiferromagnetic (AFM) coupling in core/shell nanoparticles which, in turn, leads to the foremost elucidation of positive exchange bias in bi-magnetic hard-soft systems and the remarkable regulation of the resonance field and amplitude. The AFM coupling in iron oxide-manganese oxide based, soft/hard and hard/soft, core/shell nanoparticles is demonstrated by magnetometry, ferromagnetic resonance and X-ray magnetic circular dichroism. Monte Carlo simulations prove the consistency of the AFM coupling. This unique coupling could give rise to more advanced applications of bi-magnetic core/shell nanoparticles.
日益增长的磁性器件小型化需求推动了人们对双磁纳米粒子的近期研究兴趣，将其作为最终的小型组件。主要目标之一是复制迄今为止在层状系统中观察到的实际磁性。在这种情况下，尽管已经在核/壳纳米粒子中证明了诸如交换偏置或弹簧磁铁等有用的效应，但对于器件而言，其他有趣的关键特性仍然难以捉摸。在这里，我们展示了核/壳纳米粒子中存在的强反铁磁（AFM）耦合，这反过来又导致双磁硬软系统中首次阐明了正的交换偏置，以及共振场和幅度的显著调节。通过磁强计、铁磁共振和 X 射线磁圆二色性证明了基于氧化铁-氧化锰的软/硬和硬/软核/壳纳米粒子中的 AFM 耦合。蒙特卡罗模拟证明了 AFM 耦合的一致性。这种独特的耦合可以为双磁核/壳纳米粒子的更先进应用提供可能性。
