Organic-inorganic hybrid spintronics

自旋电子学与有机材料的结合，导致了有机自旋电子学这一新领域的形成。随着分子磁阻或有机磁阻等效应的发现，以及有机自旋阀或自旋记忆阻器等器件的发现，该领域的主要焦点是通过电极对分子的作用，在由金属或铁磁导线与有机分子接触的器件中诱导功能。这种作用包括诱导分子中的自旋极化，将分子磁矩钉在衬底的磁矩上，或者通过与衬底的电子气相互作用来改变分子的状态和轨道。就在最近，我们还证明了相反的作用在揭示通过反铁磁性有序分子膜的作用而产生的钴薄膜的交换偏置方面也可以起到显著的作用。在这个项目中，我们打算扩展我们对分子在铁磁电极上作用的研究，以实现多功能器件，在这种器件中，分子的结构跃迁改变了电极的磁性。我们将提出两个主要观点。首先，可以通过电场、光或温度等外部刺激在磁性和非磁性状态之间切换的自旋交叉复合体将被交换耦合到薄铁磁层。通过改变分子的构象从而改变它们的自旋态，我们预计磁性衬底的磁矩、磁各向异性和磁滞都会有很大的变化。我们预计这种效应将通过磁弹性耦合得到增强，这要归功于分子的两个自旋态之间的大小变化。其次，利用铁电分子膜，铁磁体界面处的高电场可以引起金属磁性的变化，从而实现多铁杂化系统。这些系统将用广泛的实验技术进行研究，从扫描隧道显微镜、原子力显微镜和磁力显微镜等局部探测器，到X射线圆磁二向色性、磁光克尔效应和输运测量等空间平均技术。通过结合两个主要研究人员及其小组的技术诀窍，可以利用这种广泛的技术来精确定位这些混合系统中的相关物理相互作用。

The combination of spintronics and organic materials has recently led to the formation of the new field of organic spintronics. With the discoveries of effects like molecular magnetoresistance or organic magnetoresistance and devices like organic spin valves or spin-memristors, the main focus of the field was to induce a function in a device consisting of metallic or ferromagnetic leads in contact with organic molecules by the action of the electrodes on the molecules. This action includes effects inducing a spin-polarization in the molecules, pinning molecular magnetic moments to that of the substrate or modifying the molecular states and orbitals by the interaction with the electron gas of the substrates. Only recently, we demonstrated that also the opposite action can be of significantly size in revealing an exchange bias of thin Co films by the action of an antiferromagnetically ordered molecular film. In this project, we intend to expand our studies of the action of molecules on the ferromagnetic electrodes in order to realize multifunctional devices, in which structural transitions in molecules switch the magnetic properties of the electrodes. Two main ideas will be addressed. First, spin-crossover complexes that can be switched between a magnetic and a non-magnetic state by external stimuli like electric fields, light or temperature will be exchange coupled to thin ferromagnetic layers. By switching the conformation of the molecules and thus their spin state, we expect large changes in the magnetic moment, magnetic anisotropy and hysteresis in the magnetic substrate. We expect such effects to be enhanced by magneto- elastic coupling, thanks to the large size change between the two spin states of the molecules. Second, using ferroelectric molecular films, the high electric field at the interface to the ferromagnet can induce changes in the magnetic properties of the metal realizing a multiferroic hybrid system. The systems will be studied with a broad range of experimental techniques ranging from local probes like scanning tunnelling microscopy, atomic and magnetic force microscopy to spatially averaging techniques like X-ray circular magnetic dichroism, magneto-optical Kerr effect and transport measurements. By combining the know-how of the two principle investigators and their groups, this wide spectrum of techniques can be utilized to pinpoint the relevant physical interactions in these hybrid systems.