Magnetization processes and magnetic domain structures in Ta/CoFeB/MgO stacks

• Published in: Journal of magnetism and magnetic materials 2021-07, Vol.529, p.167699, Article 167699
• Main Authors: Dhiman, A.K., Dohi, T., Dobrogowski, W., Kurant, Z., Sveklo, I., Fukami, S., Ohno, H., Maziewski, A.
• Format: Article
• Language: English
• Subjects: Barkhausen effect; FeCoB; Kerr magnetooptical effect; Magnesium oxide; Magnetic anisotropy; Magnetic domains; Magnetic measurement; Magnetization reversal; Magnons; Nanochannels; Nucleation; perpendicular magnetic anisotropy; Stacks; Thickness
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2020.167699

•Magnetization processes and magnetic domain structures in Ta/CoFeB(1.24–1.6 nm)/MgO.•polar magneto-optical Kerr effect magnetometry and microscopy were used.•Magnetization reversal of domains structures with narrow stripes.•Magnetization after-effect described by Barkhausen length was studied.•Thickness dependence of magnetic anisotropy constants were determined. Magnetization processes and magnetic domain structures in Ta/CoFeB/MgO stacks were studied in a series of samples with various CoFeB thicknesses d ranging from 1.24 to 1.60 nm with a step of 0.04 nm, using polar magneto-optical Kerr effect (PMOKE) magnetometry and microscopy. Thickness dependence of the magnetic anisotropy was evaluated and the first and second order anisotropy constants were quantified for each thickness. Accordingly, this dependence was deduced to result in magnetization reorientation from out-of-plane to in-plane through an easy-cone magnetization region (1.39 nm ≤ d ≤ 1.41 nm) as d was increased. PMOKE imaging of the magnetization reversal processes for stacks with out-of-plane easy axis indicated both a significant increase of the density of nucleation centers and a change in domain morphology with increasing d up to the magnetization reorientation thickness. Magnetization reversal dynamics was described by a thermal activation model consistent with a Barkhausen length of about 120 nm. The thinnest films with d = 1.24 and 1.28 nm exhibited straightened narrow stripe domains resulting from magnetic dipolar repulsion. A thorough study of narrow stripe domains was performed via direct and indirect magnetization reversal processes. The application of such structures as spin wave nano-channels could be promising.