Kim Si Nyeon, Choi Jun Woo, Lim Sang Ho
Department of Materials Science and Engineering, Korea University, Seoul, 02841, Korea.
Center for Spintronics Research, Korea Institute of Science and Technology, Seoul, 02792, Korea.
Sci Rep. 2019 Feb 7;9(1):1617. doi: 10.1038/s41598-018-38269-w.
The low-field sensitivity of a giant magnetoresistance (GMR) spin valve can be enhanced by tailoring the bias field of the free layer because this sensitivity and bias field are known to show a strong correlation. In this study, the free-layer bias field is reduced considerably to almost zero via the insertion of an ultrathin nonmagnetic spacer between the pinned layer and the pinning layer. The spacer promotes an increase in the density of Néel walls in the pinned layer. This increase, in turn, induces domain-wall-induced magnetostatic interactions of the free poles formed on the Néel walls inside the free and pinned layers. The magnetostatic interactions result in the formation of flux closures that act as pinning sites during the magnetization reversal process and stabilize the antiparallel magnetization state between the free layer and the pinned layer by suppressing the switching of the free layer from the antiparallel state to the parallel state. Furthermore, the spacer offers an additional advantage of increasing the GMR ratio by inducing a specular scattering effect at its top and bottom interfaces. A highly improved low-field sensitivity of 12.01 mV/mA·Oe is achieved in the sample with a Cu/Pt dual spacer.
巨磁电阻（GMR）自旋阀的低场灵敏度可通过调整自由层的偏置场来提高，因为已知这种灵敏度与偏置场之间存在很强的相关性。在本研究中，通过在钉扎层和自由层之间插入超薄非磁性间隔层，将自由层偏置场大幅降低至几乎为零。该间隔层促使钉扎层中奈尔壁的密度增加。这种增加进而引发自由层和钉扎层内部奈尔壁上形成的自由磁极的畴壁诱导静磁相互作用。静磁相互作用导致磁通闭合的形成，这些磁通闭合在磁化反转过程中充当钉扎位点，并通过抑制自由层从反平行状态切换到平行状态来稳定自由层与钉扎层之间的反平行磁化状态。此外，该间隔层还具有另一个优势，即通过在其顶部和底部界面诱导镜面散射效应来提高巨磁电阻比。在具有Cu/Pt双间隔层的样品中实现了高达12.01 mV/mA·Oe的低场灵敏度显著提高。
