Publication Date:
2015-02-18
Description:
We demonstrate strain-induced modulation of perpendicular magnetic anisotropy (PMA) in (001)-oriented [Pb(Mg 1/3 Nb 2/3 )O 3 ] (1−x) -[PbTiO 3 ] x (PMN-PT) substrate/Ta/CoFeB/MgO/Ta structures using ferromagnetic resonance (FMR). An in-plane biaxial strain is produced by applying voltage between the two surfaces of the PMN-PT substrate, and is transferred to the ferromagnetic CoFeB layer, which results in tuning of the PMA of the CoFeB layer. The strain-induced change in PMA is quantitatively extracted from the experimental FMR spectra. It is shown that both first and second-order anisotropy terms are affected by the electric field, and that they have opposite voltage dependencies. A very large value of the voltage-induced perpendicular magnetic anisotropy modulation of ∼7000 fJ/V·m is obtained through this strain-mediated coupling. Using this FMR technique, the magnetostriction coefficient λ is extracted for the ultrathin 1.1 nm Co 20 Fe 60 B 20 layer, and is found to be 3.7 × 10 −5 , which is approximately 4 times larger than the previously reported values for CoFeB films thicker than 5 nm. In addition, the effect of strain on the effective damping constant ( α eff ) is also studied and no obvious modulation of the α eff is observed. The results are relevant to the development of CoFeB-MgO magnetic tunnel junctions for memory applications.
Print ISSN:
0003-6951
Electronic ISSN:
1077-3118
Topics:
Physics
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