Abstract
Although current in-plane giant magnetoresistance (CIP-GMR) is widely used as various magnetic field sensors, a higher magnetoresistance (MR) ratio is still required to improve their sensitivity and detectivity for certain applications. Here, we report dramatic enhancement of the MR ratio up to 26.5% in a spin valve device and 40.5% in an antiferromagnetically coupled trilayer device using fully epitaxial Co50Fe50/Cu/Co50Fe50 structures with metastable bcc-Cu spacer layers. Transmission electron microscopy analysis indicated that the metastable bcc-Cu had a perfect lattice match at the bcc-Co50Fe50/bcc-Cu interfaces. First-principles calculations showed good electronic band matching that induces a large spin asymmetry of the electron transmittance in the in-plane direction. The combination of this substantial lattice match and electronic band match is attributed to the large MR ratio, suggesting that exploring the use of metastable structure in ferromagnetic/nonferromagnetic multilayers will lead to further enhancement of CIP-GMR.
Highlights
IntroductionSince the discovery of current in-plane giant magnetoresistance (CIP-GMR) in 1988, an enormous number of the studies have been performed on this phenomena and various applications have been developed. The GMR effect was first found in ferromagnetic (FM)/nonmagnetic (NM) multilayers, in which the ferromagnetic layers magnetically interact with each other by interlayer exchange coupling through the nonmagnetic layer. The discovery of a large exchange bias effect from antiferromagnetic (AFM) materials to pin the magnetization of the ferromagnetic (FM) layers led to the development of spin valve (SV) type CIP-GMR, which allows the FM layer to switch at a small external magnetic field to be suitable for magnetic field sensor applications with high magnetic field sensitivity, such as read heads for hard disk drives (HDDs)
The discovery of a large exchange bias effect from antiferromagnetic (AFM) materials to pin the magnetization of the ferromagnetic (FM) layers led to the development of spin valve (SV) type current in-plane giant magnetoresistance (CIP-GMR),4 which allows the FM layer to switch at a small external magnetic field to be suitable for magnetic field sensor applications with high magnetic field sensitivity, such as read heads for hard disk drives (HDDs)
Multilayer and SV-type CIP-GMR devices were developed for a variety of sensing applications, including earth magnetic field sensors, speed-rotation-position sensors in automobiles,5 and detectors of magnetic beads used in biomedical applications
Summary
Since the discovery of current in-plane giant magnetoresistance (CIP-GMR) in 1988, an enormous number of the studies have been performed on this phenomena and various applications have been developed. The GMR effect was first found in ferromagnetic (FM)/nonmagnetic (NM) multilayers, in which the ferromagnetic layers magnetically interact with each other by interlayer exchange coupling through the nonmagnetic layer. The discovery of a large exchange bias effect from antiferromagnetic (AFM) materials to pin the magnetization of the ferromagnetic (FM) layers led to the development of spin valve (SV) type CIP-GMR, which allows the FM layer to switch at a small external magnetic field to be suitable for magnetic field sensor applications with high magnetic field sensitivity, such as read heads for hard disk drives (HDDs). The discovery of a large exchange bias effect from antiferromagnetic (AFM) materials to pin the magnetization of the ferromagnetic (FM) layers led to the development of spin valve (SV) type CIP-GMR, which allows the FM layer to switch at a small external magnetic field to be suitable for magnetic field sensor applications with high magnetic field sensitivity, such as read heads for hard disk drives (HDDs). Magnetic encephalography and cardiography, which require much lower noise, would be promising applications because CIP-GMR has intrinsically small 1/f noise and the device resistance is tunable.. Magnetic encephalography and cardiography, which require much lower noise, would be promising applications because CIP-GMR has intrinsically small 1/f noise and the device resistance is tunable.7,8 For all these magnetic sensing applications, a large magnetoresistance (MR) ratio is always beneficial for improving sensitivity and detectivity Multilayer and SV-type CIP-GMR devices were developed for a variety of sensing applications, including earth magnetic field sensors, speed-rotation-position sensors in automobiles, and detectors of magnetic beads used in biomedical applications. Here, magnetic encephalography and cardiography, which require much lower noise, would be promising applications because CIP-GMR has intrinsically small 1/f noise and the device resistance is tunable. For all these magnetic sensing applications, a large magnetoresistance (MR) ratio is always beneficial for improving sensitivity and detectivity
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