In-plane spin reorientation transition in Co/Py bilayers grown epitaxially on vicinal Cu(001)

Co/Py bilayers were grown epitaxially onto a vicinal Cu(001) substrate with the atomic steps parallel to the [110] crystalline axis. We show that the magnetization in vicinal Cu/Co/Py/Cu(001) undergoes an in-plane spin reorientation transition (SRT) from perpendicular to parallel direction of the steps as the Co film thickness increases. By performing Rotation Magneto-Optic Kerr Effect (ROTMOKE) measurement as a function of both the Py and the Co film thicknesses, we show that the observed in-plane SRT results from a competition between the step-induced uniaxial anisotropies in the Py and Co films that favor the Py and Co magnetizations perpendicular and parallel to the atomic steps, respectively. Step decoration experiment further shows that the uniaxial anisotropy originates from the step edges of the vicinal surface.