Rosenberger Paul, Kundu Moumita, Gloskovskii Andrei, Schlueter Christoph, Nowak Ulrich, Müller Martina
Fachbereich Physik, Universität Konstanz, 78457, Constance, Germany.
Fakultät Physik, Technische Universität Dortmund, 44221, Dortmund, Germany.
Sci Rep. 2024 Sep 16;14(1):21586. doi: 10.1038/s41598-024-70548-7.
Proximity effects allow for the adjustment of magnetic properties in a physically elegant way. If two thin ferromagnetic (FM) films are brought into contact, electronic coupling alters their magnetic exchange interaction at their interface. For a low- rare-earth FM coupled to a 3d transition metal FM, even room temperature magnetism is within reach. In addition, magnetic proximity coupling is particularly promising for increasing the magnetic order of metastable materials such as europium monoxide (EuO) beyond their bulk , since neither the stoichiometry nor the insulating properties are modified. We investigate the magnetic proximity effect at Fe/EuO and Co/EuO interfaces using hard X-ray photoelectron spectroscopy. By exciting the FM layers with circularly polarized light, magnetic dichroism is observed in angular dependence on the photoemission geometry. In this way, the depth-dependence of the magnetic signal is determined element-specifically for the EuO and 3d FM parts of the bilayers. In connection with atomistic spin dynamics simulations, the thickness of the EuO layer is found to be crucial, indicating that the observed antiferromagnetic proximity coupling is a short-ranged and genuine interface phenomenon. This fact turns the bilayer into a strong synthetic ferrimagnet. The increase in magnetic order in EuO occurs in a finite spatial range and is therefore particularly strong in the 2D limit-a counterintuitive but very useful phenomenon for spin-based device applications.
近邻效应能够以一种物理上简洁的方式实现磁性能的调控。如果将两个铁磁（FM）薄膜相互接触，电子耦合会改变它们在界面处的磁交换相互作用。对于一个与3d过渡金属铁磁体耦合的低稀土铁磁体而言，甚至在室温下也能实现磁性。此外，磁近邻耦合对于提高诸如一氧化铕（EuO）等亚稳材料的磁有序性特别有前景，因为其化学计量比和绝缘性能都不会被改变。我们使用硬X射线光电子能谱研究了Fe/EuO和Co/EuO界面处的磁近邻效应。通过用圆偏振光激发铁磁层，在光电子发射几何结构的角度依赖关系中观察到了磁二向色性。通过这种方式，针对双层结构中EuO和3d铁磁部分，以元素特异性的方式确定了磁信号的深度依赖性。结合原子自旋动力学模拟，发现EuO层的厚度至关重要，这表明所观察到的反铁磁近邻耦合是一种短程且真实的界面现象。这一事实使得双层结构成为一种强合成铁磁体。EuO中磁有序性的增加发生在有限的空间范围内，因此在二维极限下尤为显著——这对于基于自旋的器件应用来说是一种违反直觉但非常有用的现象。
