Impedance Spectroscopy Of Micron Sized Magnetic Tunnel Junctions With Mgo Tunnel Barrier

We have studied the magnetoimpedance of micron sized magnetic tunnel junction sensors with 1.7 nm MgO tunnel barrier. We performed ac impedance spectroscopy in the frequency range between 100 Hz-40 MHz as a function of applied magnetic field in the sensing direction. We model our devices with a simple RLC circuit. Fitting the model to our data results in frequency independent R, L, and C, and our low frequency results are in agreement with dc measurements. Despite excellent agreement with published result on interface capacitance for MgO barrier magnetic tunnel junctions similar to ours we do not observe any magnetocapacitance in our devices. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3449573]