Finite element modeling of the bit-resolution of EMR sensors with I+/V+/I-/V-lead geometry

Summary form only given. Extraordinary magneto-resistance (EMR) read sensors are promising candidates for high density magnetic recording as they do not contain any magnetic material. Thus, they do not suffer from magnetic noise due to thermal fluctuations at small dimensions as observed in conventional giant magnetoresistive (GMR) or tunnel-valve sensors or spin-torque noise at high current densities as observed in current perpendicular to the plane GMR sensors. We used the finite element method (FEM) to model the response of EMR sensors comprising an AlSb/InAs (12 nm)/AlSb electron quantum well structure with a sheet resistance of 300 Omega/sq and a room temperature mobility of mu = 1.6/Tesla. The EMR sensors with I+/V+/ I-/ V-lead geometry were processed by using conventional e-beam techniques. Gold was used for the leads and shunt with a contact resistance to the quantum well of about 3 times10^-6 Omegacm². The spacing between the edges of the voltage and I-leads is 100 nm. The model shows that higher signals can be achieved when the lead geometry is (I+/V+/I-/V-) as compared to the geometry originally described by Solin, et al. (I+/V+/V-/I-). Moreover, our calculations show that in this geometry an EMR sensor, although its dimension may be larger than the magnetic bit to be sensed itself, still can act as a local sensor. We further show that the response is solely determined by the spacing and positioning of the voltage leads with respect to the bit. Our FEM calculations are in good agreement with experimental data. We measured a resistance change of DeltaR~390 mOmega/Oe when exciting the whole sensor. The FEM model fits the data assuming a mobility of mu = 1 / Tesla.