Angular dependence of spin torque critical currents for CPP-GMR read heads

This paper employs (analytical) micromagnetic modeling to derive expressions for the critical current at the onset of spin-transfer-torque (STT) instability in CPP-GMR read heads, as a function of the relative angle between the free and reference layer magnetizations, including a general angular dependent STT coefficient. Experimental measurement of the angular dependence of the critical currents are made on 50-nm-sized CPP-GMR devices with synthetic antiferromagnet pinned layers, and fabricated using e-beam lithography. The results are consistent with prior theoretical models, but indicate perhaps unanticipated implications for read head operation.