Fig. 4: Experimental demonstration of curvature induced pinning of a BPDW.
From: Tailoring the energy landscape of a bloch point domain wall with curvature
a Magnetic configuration of the undulating structure after the application of magnetic fields. The upper row shows the XMCD images measured at the Co L3 edge for the same structure before saturation (I) and after applying a magnetic field sequence of −24 mT (II), −25 mT (III) −29 mT (IV), −32 mT (V) and −40 mT (VI). The XMCD signal is coming from the shadow of the structure where black and white contrast means a component of the magnetization parallel or antiparallel to the X-rays direction. The lower row shows schematics of the magnetization of the structure for each XMCD image where red indicates magnetization pointing up and blue corresponds to magnetization pointing down. The scale bar is 1 µm in all images. b Depinning field as a function of radius of curvature extracted from a sequence of experiments as the one shown in (a). c Sketch of the component of the magnetic fields with respect to the domain wall. d Component of the magnetic field parallel to the wire as a function of the radius of curvature and Zeeman energy calculated from the depinning field shown in panel b as a function of the radius of curvature. e Depinning field as a function of the cell size for a nanowire of 70 nm of diameter containing a BPDW. g Depinning field as a function of the radius of curvature for a simulated nanotube of 70 nm of diameter containing a vortex domain wall using a cell size of 4 nm. f The expected pinning of a BPDW as a function of curvature arising from the contributions of the atomic lattice (e) and the curvature (g), which qualitatively reproduces the experimental behavior in (b).
