Manipulation of free-layer bias field in giant-magnetoresistance spin valve by controlling pinned-layer thickness

• Published in: Journal of alloys and compounds 2020-05, Vol.823, p.153727, Article 153727
• Main Authors: Kim, Si Nyeon, Chung, Ku Hoon, Choi, Jun Woo, Lim, Sang Ho
• Format: Article
• Language: English
• Subjects: Bias; Crystal growth; Domain structure; Giant magnetoresistance; Magnetic measurements; Magnetic thin films and multilayers; Magnetization; Magnetoresistance; Magnetoresistivity; Sensitivity; Spin valves; Thickness
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.153727

The manipulation of the bias field of the free-layer in giant magnetoresistance spin-valves is of great importance in sensor applications because this feature dominantly affects the low-field sensitivity of magnetoresistance. In this study, it is demonstrated that the bias field of the free-layer can be manipulated by controlling the thickness of the pinned-layer deposited afterward. The key to success is the utilization of the magnetostatic interactions between the free-poles formed on the Néel walls in both free- and pinned-layers. Magnetostatic interactions play a role in stabilizing the antiparallel magnetization state and hence in suppressing the magnetization switching of the free-layer from an antiparallel to a parallel state. A nearly zero bias field is achieved for a Ta-buffered sample with a pinned-layer thickness of 1.75 nm, where a very high low-field sensitivity of 7.7 mV/mA·Oe is obtained. •The free-layer bias field is considerably reduced to a nearly zero value by controlling the pinned-layer thickness.•The key to the success is the utilization of domain wall-induced magnetostatic interactions between Néel walls in both free- and pinned-layers.•A strong negative correlation exists between the free-layer bias field and low-field sensitivity.•The low-field sensitivity is achieved to be as high as 7.7 mV/mA·Oe.