Structural and Magnetic Properties of CoPd Alloys for Non-Volatile Memory Applications

Abstract

We have intensively studied perpendicular magnetic anisotropy (PMA) CoPd alloys, both structurally and magnetically, as a simple means of pinning MgO-based perpendicular magnetic tunnel junctions (pMTJs) for spin-transfer torque magnetic tunnel junction (STT-MRAM) applications. A compositional study of the Co x Pd100-x alloys at 50 nm thickness showed that the maximum coercivity and anisotropy was found for Co 25 Pd 75 . Perpendicular magnetic tunnel junction stacks were deposited using different compositions of CoPd. Current-in-plane tunneling measurements indicated that the TMR values roughly correlated with the coercivity and anisotropy of the single layers. A thickness study indicated that the alloy was fully perpendicular for thicknesses as low as 20 nm. Various seed layers were employed to optimize the coercivity of the Co 25 Pd 75 layer. Magnetometry, X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies were carried out to relate the magnetic and structural properties of these layers.