Low Gilbert Damping Constant in Perpendicularly Magnetized W/CoFeB/MgO Films with High Thermal Stability.

ABSTRACT: Perpendicular magnetic materials with low damping constant and high thermal stability have great potential for realizing high-density, non-volatile, and low-power consumption spintronic devices, which can sustain operation reliability for high processing temperatures. In this work, we study the Gilbert damping constant (?) of perpendicularly magnetized W/CoFeB/MgO films with a high perpendicular magnetic anisotropy (PMA) and superb thermal stability. The ? of these PMA films annealed at different temperatures (Tann) is determined via an all-optical Time-Resolved Magneto-Optical Kerr Effect method. We find that ? of these W/CoFeB/MgO PMA films decreases with increasing Tann, reaches a minimum of ??=?0.015 at Tann?=?350?°C, and then increases to 0.020 after post-annealing at 400?°C. The minimum ? observed at 350?°C is rationalized by two competing effects as Tann becomes higher: the enhanced crystallization of CoFeB and dead-layer growth occurring at the two interfaces of the CoFeB layer. We further demonstrate that ? of the 400?°C-annealed W/CoFeB/MgO film is comparable to that of a reference Ta/CoFeB/MgO PMA film annealed at 300?°C, justifying the enhanced thermal stability of the W-seeded CoFeB films.

SUBMITTER: Lattery DM 

PROVIDER: S-EPMC6127240 | biostudies-other | 2018 Sep

REPOSITORIES: biostudies-other