Depth-resolved magnetization profile of MgO/CoFeB/W perpendicular half magnetic tunnel junctions

V. Bansal (1) , J.-M. Tonnerre (1) , E. Mossang (2) , L. Ortega (3) , F. Fettar (1) , J. Chatterjee (4) , S. Auffret (4) , I.-L. Prejbeanu (4) , B. Dieny (4)

1 NEEL - SIN - Surfaces, Interfaces et Nanostructures
2 NEEL - X'Press - X'Press : diffraction et hautes pressions
3 LPS - Laboratoire de Physique des Solides
4 SPINTEC - SPINtronique et TEchnologie des Composants

In this work, we used the soft X-ray resonant magnetic reflectivity to study the depth-resolved out-of-plane ( oop) magnetization profile of a CoFeB/MgO sample with W/Ta cap layer after annealing at 400°C. It is a powerful technique to probe buried magnetic interfaces of ultra-thin films by combining the depth-resolved information of X-ray reflectivity with the species selectivity of X-ray magnetic circular dichroism. It allowed us to resolve the oop magnetization within a 1.36 nm thick CoFeB layer by the measurement of angle-dependent specular reflectivity at large scattering angles (up to 80°). We determined a graded magnetic distribution for both Fe and Co with a 20% increase at the interface with MgO, decreasing slightly over a thickness of 0.7 nm from MgO before it rapidly decreases to 50% at the interface with W. After applying a non-saturating magnetic field in the plane of the sample, we also quantified a similar magnetization profile with an inclined moment configuration. This indicates that the magnetization gradient is a robust property of the CoFeB layer in the studied sample.

Domaines: Physique [physics]

V. Bansal, J.-M. Tonnerre, E. Mossang, L. Ortega, F. Fettar, et al.. Depth-resolved magnetization profile of MgO/CoFeB/W perpendicular half magnetic tunnel junctions. AIP Advances, 2022, 12 (3), pp.035129. ⟨10.1063/9.0000343⟩. ⟨hal-03760609⟩