Speaker
Description
$\quad$ The magnetoelectric (ME) effect utilizes strain-mediated coupling between magnetostrictive and piezoelectric layers for electric-field control of magnetization and magnetic-field control of strain. Recently, ME effect has gained attention due to its wide range of applications in magnetic field sensors, spintronic and RF devices. Hence, it is vital to understand how various parameters influence the coupling between piezoelectric and magnetostrictive layers for the improvement of ME devices.
$\quad$ In this work, the influence of the residual stress induced during depostion of AlScN(500nm) layer on a 10 nm thick Co$_{40}$Fe$_{40}$B$_{20}$ magnetostrictive layer was investigated. AlScN was selected as the piezoelectric material due to its compatibility with the standard CMOS processes. Although CoFeB has been extensively studied in conjunction with other piezoelectric substrates 1, its behaviour when interfaced with AlScN remains unclear.
$\quad$ To characterize the presence of in-plane magnetic anisotropy in the CoFeB layer grown on top of AlScN, hysteresis loops were measured using a vibrating sample magnetometer (VSM) by varying azimuthal in-plane angle (φ). The polar plot of coercivity (Hc) vs φ shown in fig. 1 confirmed the presence of stress induced uniaxial anisotropy (along φ = 60°) in case of AlScN/CoFeB/Ta ME stack. Atomic force microscopy (AFM) revealed the presence of abnormally oriented grains (AOGs) in the AlScN layer (fig. 2). The increased coercive field near the hard axis (along φ = 150°) is attributed to the misalignment of local grain anisotropy 2. The influence of different seed layers such as Ta and Pt was also studied (fig. 1). The results presented here are the first steps for further development of high-quality magnetoelectric composites and the future direct integration of ME devices with CMOS technology.
Fig. 1 Polar plot of Coercivity (Hc) vs φ of AlScN/x/CoFeB/Ta stack (x= No seed layer/Ta/Pt)
Acknowledgements
This work has received funding from the European Union under the MSCA COFUND project CRYSTALLINE, grant agreement no. 101126571.
References
1 Millo, Florian, et al. "Symmetry of the dissipation of surface acoustic waves by ferromagnetic resonance." AIP Advances 15.4 (2025).
2 Idigoras, O., et al. "Collapse of hard-axis behavior in uniaxial Co films." Physical Review B—Condensed Matter and Materials Physics 84.13 (2011): 132403.