Absence of magnetic state dependent low-frequency noise in spin-valve systems

The low-frequency noise in magnetic tunnel junctions and giant magnetoresistance devices in various magnetic states has been investigated. The noise measurements in both types of devices show a 1/f spectrum in either the parallel or antiparallel magnetic state. The noise as the magnetization switches from parallel to antiparallel and vice versa in the transition regions (characterized by a large dR/dH), in which the magnetic aftereffect is present and the system is out of equilibrium, also exhibits a 1/f spectrum of a magnitude consistent with that in the parallel and antiparallel states where the system relaxes to the equilibrium state. Included is how even small magnetic aftereffect signals can replicate the results of many previous studies. Two additional experiments are described which set an upper limit for the magnetic noise in the devices investigated.