Perpendicular Magnetic Anisotropy in Pt/Co/AlO Trilayer Structures Depending on AlO Thickness and Fabrication Method

We investigate the perpendicular magnetic anisotropy dependence on the AlO capping layer in Pt/Co/AlO films. AlO was deposited on Pt/Co films by RF magnetron sputtering and atomic layer deposition (ALD) with varying thickness. It is found that the prolonged deposition of thick AlO layers by RF magnetron sputtering causes significant damage to the Pt/Co underneath while AlO layers formed by ALD can be of arbitrary thickness with no damage to the magnetic properties of the films. The decline of the magnetic properties can be attributed to the method of AlO deposition for each process. In the RF magnetron sputtering, AlO atoms with high kinetic energy are ejected from a sputter target resulting in the degradation of Pt/Co films, while the process of deposition of AlO by ALD is governed by a series of chemically reactive condensations allowing for arbitrary deposition thickness of AlO.