Perpendicular magnetic tunneling junction with double barrier layers for MRAM application

A double-barrier-layer perpendicular magnetic tunneling junction (DpMTJ) structure consisting of Si substrate/Pt/GdFeCo/AlOx/ GdFeCo/FeCo/AlOx/FeCo/TbFeCo/Pt/Ti-cap was prepared by a direct current (dc) and radio frequency (RF) magnetron sputtering method. An elliptical DpMTJ element with 3.5 mu m x 2.5 mu m size was fabricated using a top-down technique. A conducting atomic force microscope (CAFM) was used to obtain I-V curves of DpMTJ structures. We obtained the magnetoresistance (MR) ratio value from measured I-V curves by applying two opposite magnetic fields value of +/- 200 Oe perpendicular to the plane of film. The MR ratio was reached as high as 74% at zero applied bias voltage. Furthermore, the MR ratio decreased as bias voltage increased. It could make the DpMTJ structure to be used in the high-density MRAM devices.