Tuning of MgO barrier magnetic tunnel Junction bias current for picotesla magnetic field detection

摘要

Two sets of low resistance MgO junctions were patterned into junctions with areas from 1 to 24 mu m~2. By properly choosing the operating conditions the background noise can be placed at the level of equivalent fields of approx 10~(-11) and approx 10~(-12) T/Hz~(0.5) calculated for 30 Oe linear range junctions of types 1 (150 OMEGA mu m~2, tunnel magnetoresistance (TMR) = 150 percent) and 2 (30 OMEGA mu m~2, TMR = 100 percent), respectively. Such room temperature sensitivities can only be achieved at frequencies where the 1// noise contribution is negligible. From the 1/f noise Hooge constant (alpha_H=2.66 X 10~(-9) mu m~2 at R X A approx 150 OMEGA mu m~2 and alpha_H = 1.24 X 10~(-9) mu m~2 at R X A approx 30 OMEGA mu m~2) the 1/f noise corner in the optimum biasing conditions is predicted to be located between 10 and 70 MHz, depending on junction area and resistance.