Strain Induced Depth Dependent Magnetization Variation in Co thin films on PMN-PT Studied Using Polarized Neutron Reflectometry (PNR)*

Strain induced clocking of nanomagnetic computing devices, often termed as “Straintronic devices” are inherently non-volatile and can be switched with ultra-low energy consumption [1-3]. These are nanoscale heterostructures of piezoelectric/ magnetostrictive materials. Electric field applied in the piezoelectric layer generates a strain which is transferred to the magnetostrictive layer inducing magnetization rotation. Variation in the transferred strain from the piezoelectric layer along the thickness of the magnetostrictive layer may lead to variation in magnetization rotation. This work studied this depth dependent magnetization variation in magnetostrictive Co films of 60 nm thickness on PMN-PT (001) substrates (1cm x 1cm x 0.5 mm) using PNR. PNR Measurements under different applied magnetic fields (saturation, remanence and near coercive field) and electric fields (0-400V) confirmed depth dependent magnetization rotation. Maximum rotation occurred near the PMN-PT/ Co interface and decreased towards the Co surface, which is reflective of the strain transfer simulated in COMSOL.
1. Nano Lett. 16, 1069 (2016). 2. Phys. Rev. Lett. 111, 027204 (2013). 3. Nano Lett. 10, 1219 (2010). 4. http://www.ncnr.nist.gov/reflpak.