Exchange bias is a physical effect that is used in many spintronic devices like magnetic read heads, magnetic random access memories, and most kinds of magnetic sensors. For the next generation of fully organic devices, molecular exchange bias, if existing, could have a huge impact for developing mechanically soft and environment friendly devices. The observation of molecular exchange bias has been reported recently in hybrid systems where a metallic ferromagnet is exchanged biased by an organic film, and it is considered to be a spinterface effect. To understand this effect, we investigate if the molecular exchange bias exists in Co/metal tetra-phenyl porphyrin hybrid bilayer systems. The molecular exchange bias is never observed when the samples are properly encapsulated, and when the exchange bias is eventually observed, it is not a spinterface effect, but it results from air-driven partial oxidation of the cobalt film transforming part of the metallic cobalt into a cobalt oxide that is well known to induce exchange bias effects. Surprisingly, oxidation is very difficult to prevent even by using very thick metallic encapsulating layers. A similar effect is observed in the Co/metal-phthalocyanine bilayer system, showing that the molecular exchange bias is not a spinterface effect also in the hybrid system in which this effect was originally discovered.

中文翻译：

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有机/铁磁体界面处的交换偏差可能不是自旋界面效应

交换偏置是一种物理效应，用于许多自旋电子设备，如磁读头、磁随机存取存储器和大多数类型的磁传感器。对于下一代全有机器件，如果存在分子交换偏差，可能会对开发机械柔软和环境友好的器件产生巨大影响。最近在混合系统中报告了分子交换偏压的观察，其中金属铁磁体被有机膜交换偏压，这被认为是自旋界面效应。为了理解这种效应，我们研究了钴/金属四苯基卟啉杂化双层系统中是否存在分子交换偏差。当样品被正确封装时，永远不会观察到分子交换偏差，当最终观察到交换偏差时，这不是纺丝界面效应，而是由空气驱动的钴膜部分氧化将部分金属钴转化为众所周知的氧化钴引起的交换偏压效应的结果。令人惊讶的是，即使使用非常厚的金属封装层，也很难防止氧化。在钴/金属酞菁双层系统中观察到类似的效果，表明分子交换偏向不是旋转界面效应，在最初发现这种效应的混合系统中也是如此。