Frontier of Spintronics and Magnetic Sensing Workshop

A technique of low-energy proton irradiation has succeeded in increasing perpendicular magnetic anisotropy (PMA) of phase-transformed Co/Pd superlattice and confirmed to provide a capability of achieving a magnetic recording density over 2.5 Tb/in2 [1]. Our x-ray magnetic circular dichroism study confirmed that the strong PMA is originated from an increase in the out-of-plane component of spin-orbit coupling at the interface between the phase-transformed Co and the metallic Pd layers; the orbital to spin moment ratio was increased by ~30% after proton irradiation, meaning that the increase in spin-orbit coupling is responsible for the PMA. We also found by ac measurements that the Co/Pd superlattice phase-transformed by proton irradiation shows a damping-like and a field-like torque an order of magnitude larger than all the metallic superlattice. As a result, such a large spin-orbit torque was finally able to switch this Co/Pd superlattice having an Hk of 3 T without an additional external magnetic field. In this presentation, we report and discuss this giant spin-orbit torque found in our phasetransformed superlattice. [1] S. Kim et al., Nature Nanotechnology 7, 567 (2012); S. Kim et al., ACS Nano 8, 4698 (2014). TMR sensors: from industrial to biomedical applications P.P.Freitas , S Cardoso , and R.Ferreira 1 INL and INESC MN, Portugal TMR sensors are gradually becoming an alternative to more conventional technologies (Hall effect, AMR, and even GMR), for their higher sensitivity and correspondent larger output, large field span (from 10pT at few Hz to 50 mT), adaptable impedance, low power consumption, large bandwidth response, and offering also the possibility of monolithic integration with CMOS wafers, and with flexible polyimide substrates. GMR sensors can be an option for low frequency operation where TMR sensors show higher 1/f noise. For industrial sensing, application examples will be shown for scanning probes (current, magnetic nanoparticle, magnetic material imaging) and for non-destructive testing of conductive materials where S/N in critical but is often dominated by materials noise. In the biomedical application area, we will discuss new applications of multiplexed magnetoresistive biochip technology to biomarker detection (as a protein chip, biomarker detection for brain ischemia patients), as well as Circulating Tumour Cell detection in blood using our integrated spintronic cytometer. Finally, results will be shown for TMR/GMR sensors integrated in neural probes (SOI and thin Si wafers) and used to record magnetic fields generated in the visual cortex of a cat. Interlayer Exchange Coupling in Low RA Magnetic Tunnel Junctions