Size Dependence of Magnetic Properties of Nanoscale CoFeB–MgO Magnetic Tunnel Junctions with Perpendicular Magnetic Easy Axis Observed by Ferromagnetic Resonance

Abstract

The junction diameter D dependence of effective magnetic fields in a recording layer of CoFeB–MgO magnetic tunnel junctions with perpendicular magnetic easy axis is evaluated by ferromagnetic resonance measurements using the homodyne detection technique. The effective perpendicular magnetic field increases with decreasing D, which reflects mainly the reduction of the demagnetizing factor normal to the film plane. The stray field from a reference layer also increases with reducing D, which is in agreement with the D dependence of the shift field of the center of minor resistance versus perpendicular magnetic field curves with respect to zero magnetic field.