Effective anisotropy field in the free layer of patterned spin-valve resistors

In this work, the effective anisotropy H eff in the free layer of patterned spin-valve resistor has been investigated. A magnetic analysis is first conducted to explain the effective anisotropy, a mixed effect of the uniaxial anisotropy and the shape anisotropy. The experiment is then performed to verify the model analysis. The effective anisotropy H eff is found to be inversely proportional to the resistor linewidth, and can be modified by controlling the orientation of the axis of the uniaxial anisotropy relative to the resistor length, therefore providing a method of modifying the device sensitivity. The sensitivity is higher when spin valve is patterned with the free layer easy axis parallel rather than perpendicular to the resistor length.