Yıldırım Oğuz, Hilliard Donovan, Arekapudi Sri Sai Phani Kanth, Fowley Ciarán, Cansever Hamza, Koch Leopold, Ramasubramanian Lakshmi, Zhou Shengqiang, Böttger Roman, Lindner Jürgen, Faßbender Jürgen, Hellwig Olav, Deac Alina M
Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research , Bautzner Landstr. 400 , 01328 Dresden , Germany.
Empa-Swiss Federal Laboratories for Materials Science and Technology , Ueberlandstr. 129 , 8600 Dübendorf , Switzerland.
ACS Appl Mater Interfaces. 2020 Feb 26;12(8):9858-9864. doi: 10.1021/acsami.9b13503. Epub 2020 Feb 17.
Interfaces separating ferromagnetic (FM) layers from non-ferromagnetic layers offer unique properties due to spin-orbit coupling and symmetry breaking, yielding effects such as exchange bias, perpendicular magnetic anisotropy, spin-pumping, spin-transfer torques, and conversion between charge and spin currents and vice versa. These interfacial phenomena play crucial roles in magnetic data storage and transfer applications, which require the formation of FM nanostructures embedded in non-ferromagnetic matrices. Here, we investigate the possibility of creating such nanostructures by ion irradiation. We study the effect of lateral confinement on the ion-irradiation-induced reduction of nonmagnetic metal oxides (e.g., antiferro- or paramagnetic) to form ferromagnetic metals. Our findings are later exploited to form three-dimensional magnetic interfaces between Co, CoO, and Pt by spatial-selective irradiation of CoO/Pt multilayers. We demonstrate that the mechanical displacement of O atoms plays a crucial role in the reduction from insulating, non-ferromagnetic cobalt oxides to metallic cobalt. Metallic cobalt yields both perpendicular magnetic anisotropy in the generated Co/Pt nanostructures and, at low temperatures, exchange bias at vertical interfaces between Co and CoO. If pushed to the limit of ion-irradiation technology, this approach could, in principle, enable the creation of densely packed, atomic-scale ferromagnetic point-contact spin-torque oscillator (STO) networks or conductive channels for current-confined-path-based current perpendicular-to-plane giant magnetoresistance read heads.
将铁磁（FM）层与非铁磁层分隔开的界面由于自旋轨道耦合和对称性破缺而具有独特的性质，会产生诸如交换偏置、垂直磁各向异性、自旋泵浦、自旋转移力矩以及电荷与自旋电流之间的相互转换等效应。这些界面现象在磁数据存储和传输应用中起着关键作用，而这些应用需要在非铁磁基体中形成嵌入的FM纳米结构。在此，我们研究通过离子辐照创建此类纳米结构的可能性。我们研究横向限制对离子辐照诱导的非磁性金属氧化物（例如反铁磁或顺磁氧化物）还原以形成铁磁金属的影响。我们的研究结果随后被用于通过对CoO/Pt多层膜进行空间选择性辐照，在Co、CoO和Pt之间形成三维磁性界面。我们证明，O原子的机械位移在从绝缘的非铁磁钴氧化物还原为金属钴的过程中起着关键作用。金属钴在生成的Co/Pt纳米结构中产生垂直磁各向异性，并且在低温下，在Co和CoO之间的垂直界面处产生交换偏置。如果将这种方法推向离子辐照技术的极限，原则上可以创建密集堆积的、原子尺度的铁磁点接触自旋扭矩振荡器（STO）网络或用于基于电流限制路径的电流垂直于平面巨磁阻读头的导电通道。
