Analytical approach to driving efficiency in yoke GMR heads

In this paper, an analytical model has been established to calculate the driving efficiency, xi, which is defined as the ratio of the current-induced field at the center of the free layer in the GMR sensor to the currents in the conductors. Expressions for the driving efficiencies xi of the bias conductor and the sense conductor inside the yoke GMR test structures are derived. The trends of the driving efficiency as a function of several head parameters are obtained. The simulation results indicate that the driving efficiency of the sense current Is about an order of magnitude less than that of the bias conductor and that the product of the GMR sensor permeability and its thickness plays an important role in determining the driving efficiency. Output signal of a yoke GMR sensor calculated from this model is in good agreement with the experimental result [1].