“Nano-Barber poles”: Helical surface magnetization in nanowires

Nanomagnetism is nowadays expanding into three dimensions, triggered by the discovery of new magnetic phenomena and their potential use in applications. This shift towards 3D structures should be accompanied by strategies and methodologies to map the tridimensional spin textures associated.

A new study fruit of a collaboration of researchers from two beamlines at ALBA Synchrotron (CIRCE and MISTRAL), with the participation of the Universidad Complutense de MadridIMDEA Nanociencia and the Universidad de Salamanca shows that cylindrical nanowires have at the center a magnetization aligned with the axis of the wire and at the surface a magnetization that describes helical lines as the barber poles. The helicity provides chirality to the magnetic configuration since it can be right or left-handed. Researchers found out that two adjacent magnetic domains having opposite chirality are more difficult to move than two adjacent domains with the same chirality. This result evidences the role of the chirality on the dynamics of the domain walls that might be used as a practical variable for magnetic data storage.

Read more on the ALBA website

Image: Figure. (Left) Barber pole illustrating the helical lines that the magnetization describes at the surface of the wires. (Right) Schematics of the configuration of the magnetization of the initial state of the nanowire together with the magnetic images before and after the application of magnetic field pulses. In the initial state, the two domain walls signaled with orange arrows separate domains with the same chirality. Note that the head-to-head or tail-to-tail domains have the same chirality in spite of having opposite signs of surface magnetization. The green arrow separates two domains of different chirality since while having the same axial orientation, the surface helicity is opposite. Magnetic field pulses of 120 mT move the walls separating domains with the same chirality but not the green wall separating opposite chirality.