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

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 similar to 10(-11) and similar to 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%) and 2 (30 Omega mu m(2), TMR=100%), respectively. Such room temperature sensitivities can only be achieved at frequencies where the 1/f noise contribution is negligible. From the 1/f noise Hooge constant (alpha(H)=2.66x10(-9) mu m(2) at RxA similar to 150 Omega mu m(2) and alpha(H)=1.24x10(-9) mu m(2) at RxA similar to 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. (C) 2006 American Institute of Physics.