Half-metal CPP GMR sensor for magnetic recording

• Simulated electron transport in half-metal multilayer system to explore the CPP GMR and film stacking dependence.
• Experimentally demonstrated extremely large CPP GMR of up to 75% on epitaxial growth of Heusler films and stacks, manifesting large potential of this technology.
• Developed Heusler alloy based CPP GMR spin valves and sensors, with large CPP GMR and large DRA for magnetic recording.
• Demonstrated enhanced reader performance targeting the areal recording density of 800 Gb/in2 and beyond.

Current-perpendicular-to-plane (CPP) giant magnetoresistance in magnetic CoFeMnSi Heusler alloy based spin valves and its potential application for high areal density recording are investigated, given that film stack design and crystalline structure matching during film growth are considered. Modeling of electron transport in spin valves predicts the CPP GMR of up to 130% and 25% in pseudo and antiferromagnet pinned spin valves at large bulk diffusive scattering asymmetry in Heusler alloy layers. Experimentally, the testing structures of pseudo spin valves, which have the L21 ordered Huesler alloy layers grown on single crystal MgO substrates, were built and demonstrate the CPP GMR of 55% or larger with ΔRA≥27.5 mΩ μm2. CPP GMR reader sensors were fabricated based on antiferromagnet pinned spin valves using the same Huesler alloy materials albeit on AlTiC wafers, with narrow track widths of down to 35 nm. The CPP GMR obtained is up to 13% (18%, ΔRA=9.0 mΩ μm2 after correction of current distribution in device). Reader test results show that the low frequency track averaged output amplitude is 3.14 mV with the electrical SNR=28 dB. These read heads have the transition width of readback waveform T50 of ~22 nm and the magnetic read track width of 35.6 nm. The obtained on-track bit error rate is close to 10−3 decade at a linear density of 1800 KFCI, potentially realizing a magnetic recording with an areal density of up to 800 Gb/in2.