Design and performance of domain wall displacing-type field sensors using a magnetic tunnel junction and a giant magnetoresistive device

We report a new type of field sensor, which utilizes the oscillatory domain wall displacement in the ferromagnetic free layer to detect an external field. The sensor consists of a 1200 × 100 µm 2 Al conducting wire placed on a spin-valve giant magnetoresistive (GMR) or magnetic tunnel junction. By transmitting an alternating current through the Al conducting wire, an ac field can be generated to oscillate the domain wall in the free layer. The oscillatory domain wall displacement reduces the influence of wall coercivity and Barkhausen effect, and enables the sensor to detect the magnetic field which is much smaller than the wall coercivity. The field sensitivities of the domain wall displacing-type GMR and tunnel magnetoresistive (TMR) sensors are 2.73 mV V −1 Oe −1 and 5.81 mV V −1 Oe −1 , respectively.