Migliorini A, Kuerbanjiang B, Huminiuc T, Kepaptsoglou D, Muñoz M, Cuñado J L F, Camarero J, Aroca C, Vallejo-Fernández G, Lazarov V K, Prieto J L
Instituto de Sistemas Optoelectrónicos y Microtecnología-ISOM. Universidad Politécnica de Madrid, Avenida Complutense 30, 28040 Madrid, Spain.
Department of Physics, University of York, York YO10 5DD, UK.
Nat Mater. 2018 Jan;17(1):28-35. doi: 10.1038/nmat5030. Epub 2017 Nov 20.
Most of the magnetic devices in advanced electronics rely on the exchange bias effect, a magnetic interaction that couples a ferromagnetic and an antiferromagnetic material, resulting in a unidirectional displacement of the ferromagnetic hysteresis loop by an amount called the 'exchange bias field'. Setting and optimizing exchange bias involves cooling through the Néel temperature of the antiferromagnetic material in the presence of a magnetic field. Here we demonstrate an alternative process for the generation of exchange bias. In IrMn/FeCo bilayers, a structural phase transition in the IrMn layer develops at room temperature, exchange biasing the FeCo layer as it propagates. Once the process is completed, the IrMn layer contains very large single-crystal grains, with a large density of structural defects within each grain, which are promoted by the FeCo layer. The magnetic characterization indicates that these structural defects in the antiferromagnetic layer are behind the resulting large value of the exchange bias field and its good thermal stability. This mechanism for establishing the exchange bias in such a system can contribute towards the clarification of fundamental aspects of this exchange interaction.
先进电子学中的大多数磁性器件都依赖于交换偏置效应，这是一种将铁磁材料和反铁磁材料耦合在一起的磁相互作用，会导致铁磁滞回线单向位移一个称为“交换偏置场”的量。设置和优化交换偏置需要在磁场存在的情况下冷却至反铁磁材料的奈尔温度。在此，我们展示了一种产生交换偏置的替代过程。在IrMn/FeCo双层膜中，IrMn层在室温下发生结构相变，在其传播过程中对FeCo层产生交换偏置。一旦该过程完成，IrMn层包含非常大的单晶颗粒，每个颗粒内有大量结构缺陷，这些缺陷由FeCo层促成。磁性表征表明，反铁磁层中的这些结构缺陷是产生较大交换偏置场值及其良好热稳定性的原因。在这样一个系统中建立交换偏置的这种机制有助于阐明这种交换相互作用的基本方面。
