X-ray diffraction analysis and Monte Carlo simulations of CoFeB-MgO based magnetic tunnel junctions

Here, we present the x-ray diffraction (XRD) analysis of a pseudo spin valve (P-SV): CoFeB/MgO/CoFeB and an exchange bias spin valve (EB-SV): PtMn/CoFe/Ru/CoFeB/MgO/CoFeB magnetic tunnel junctions where the composition of CoFeB was (Co52Fe48)75B25. In the P-SV, CoFeB layers crystallized into a highly bcc (001)-oriented CoFe texture while in the EB-SV, CoFeB crystallized into both (001)-oriented and (110)-oriented textures. Moreover, CoFeB crystallized better into the (001)-oriented texture when deposited on MgO than on a Ru layer. The P-SV and EB-SV devices with layer structures equivalent to the XRD samples, showed tunneling magnetoresistance of 240% and 180%, respectively. The Ru and Ta buffer layers annealed at 340 °C mixed at the interface. The simulated crystalline structure and calculated θ-2θ profiles, using kinematical theory of x-ray scattering, correlated very well with the experimental profiles and confirmed Ta-Ru intermixing.