Dresden 2009 – scientific programme

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DS: Fachverband Dünne Schichten

DS 20: Amorphous Thin Magnetic Films

DS 20.4: Talk

Wednesday, March 25, 2009, 17:15–17:30, GER 37

Long range order on atomic scale induced at CoFeB/MgO interfaces — •Gerrit Eilers¹, Marvin Walter¹, Kai Ubben¹, Henning Ulrichs¹, Michael Seibt², Andy Thomas³, Günter Reiss³, and Markus Münzenberg¹ — ¹I. Phys. Inst., Universität Göttingen — ²IV. Phys. Inst., Universität Göttingen — ³Physics Department, Bielefeld University

Magnetic tunnel junctions (MTJs) based on amorphous (a-) CoFeB / crystalline (c-)MgO / a- CoFeB trilayers have been of great interest in research just recently. Due to their high tunnel magneto resistance (TMR) they are a promising candidate spin torque MRAM devices. For future writing concepts like current induced magnetic switching MTJs with thin barriers are necessary to provide sufficient high current densities. Therefore, the quality of the interfaces is of great significance and should be optimized on the nano-scale. The a- CoFeB / c- MgO interface has been studied by means of quantitative high resolution transmission electron microscopy (HRTEM) from atomic to micrometer length scales with increasing annealing temperatures. On the micron scale crystallisation is governed by nucleation processes. On the atomic scale a long range order is induced by the MgO interface, explaining the high TMR values >100% even for not fully crystallized CoFeB/ MgO/ CoFeB tunnel junctions. We compared the subnanometer atomic order induced at the interface with a simulated HRTEM data set generated by a multislice method from a two dimensional atomic distribution function.

Research was funded by DFG, SFB 602