Half-metal CPP GMR sensor for magnetic recording

Abstract

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≥27.5mΩμm2. 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 35nm. The CPP GMR obtained is up to 13% (18%, ΔRA=9.0mΩμm2 after correction of current distribution in device). Reader test results show that the low frequency track averaged output amplitude is 3.14mV with the electrical SNR=28dB. These read heads have the transition width of readback waveform T50 of ~22nm and the magnetic read track width of 35.6nm. The obtained on-track bit error rate is close to 10−3 decade at a linear density of 1800KFCI, potentially realizing a magnetic recording with an areal density of up to 800Gb/in2.