Magnetoresistance in Ni80Fe20/Cu/Ni80Fe20/Fe50Mn50 spin valves with low coercivity and ultrahigh sensitivity

Abstract

We present magnetoresistance measurements on Ni80Fe20/Cu/Ni80Fe20/Fe50Mn50 spin valves with crossed anisotropies: the easy magnetization direction of the unbiased Ni80Fe20 layer is perpendicular to the exchange biasing field which effectively works on the second Ni80Fe20 layer due to the interaction with the Fe50Mn50 layer. The hysteresis in the low-field magnetoresistance is less than 0.03 kA/m, which is ten times smaller than the hysteresis for similar materials with parallel anisotropies. The sensitivity (∂R/R∞)/∂H ranges from 8% to 18%/(kA/m), depending on the preparational method. To our knowledge this combination of very high sensitivity and very low coercivity has not been reported before.