Abstract
High field linear magnetoresistance is an important feature for magnetic sensors applied in magnetic levitating train and high field positioning measurements. Here, we investigate linear magnetoresistance in Pt/FePt/ZnO/Fe/Pt multilayer magnetic sensor, where FePt and Fe ferromagnetic layers exhibit out-of-plane and in-plane magnetic anisotropy, respectively. Perpendicular anisotropy L10-FePt reference layer with large coercivity and high squareness ratio was obtained by in situ substrate heating. Linear magnetoresistance is observed in this sensor in a large range between +5 kOe and −5 kOe with the current parallel to the film plane. This L10-FePt based sensor is significant for the expansion of linear range and the simplification of preparation for future high field magnetic sensors.
Highlights
Research on spintronics is fast developing due to its widely practical application [1,2,3,4]
Magnetic tunnel junctions and magnetic spin valves as the important contents in spintronics are popularly used as magnetic sensors, such as magnetic read heads for hard-disk drive, position, and speed detectors in low magnetic field measurement [5, 6]
Perpendicular anisotropy L10-FePt reference layer and in-plane anisotropy Fe free layer separated by ZnO barrier layer are perpendicular to each other
Summary
Research on spintronics is fast developing due to its widely practical application [1,2,3,4]. An approach of making a high field linear magnetic field response is to use a sandwich structure with a reference layer having high perpendicular magnetic anisotropy and an in-plane anisotropy free layer [16,17,18,19] Some problems such as narrow linear range and complicated design are still unresolved. The MR curve is nearly linear when the applied field is in the range ±5 kOe measured at 300 K, which is improved greatly compared to previously reported results [18] This design simplifies effectively the structure of linear magnetic sensors through applying L10-FePt with a large Hc as reference layer
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