Microstructure and exchange coupling parameters of MTJ with CoFeB bottom electrode

In this study, we report the relationship between interface roughness, texture and the exchange bias and the interlayer‐Néel coupling fields of the spin‐valve magnetic tunnel junction (SV‐MTJ). SV‐MTJs with the structure: Si(100)/SiO2/buffer/IrMn/CoFeB/AlOx /NiFe/Ta were deposited on two buffers: Cu and Ta/Cu/Ta/Cu, and next the samples were annealed in vacuum and in a magnetic field. XRD analysis reveals that the texture degree of MTJ with Cu buffer is significantly lower than that of the sample with Ta/Cu/Ta/Cu buffer. The enhancement of IrMn and CoFeB texture leads to a higher amplitude of roughness and an increase of exchange bias and Néel coupling fields. The comparison of junctions with CoFe and CoFeB bottom electrodes shows that addition of 5% B in a CoFe layer makes the surface of the pinned layer smoother. This leads to a lower Néel coupling field, which is desirable for application of MTJ in MRAM technology. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)