Artificial double-helix for geometrical control of magnetic chirality

A study published in ACS Nano demonstrated the imprinting of complex 3D chirality at the nanoscale using state-of-the-art fabrication techniques and magnetic microscopy at MISTRAL beamline of the ALBA Synchrotron. The results prove the possible control of the magnetic configuration with geometrical morphologies displaying 3D chirality and open a new avenue on applied nanomagnetism. The research was the result of a multiple collaboration of scientists from Cambridge, Glasgow and Zaragoza Universities, the ALBA Synchrotron and the Lawrence Berkeley Laboratory.

An object is chiral if its image in a mirror cannot bring to coincide with itself as our right and left hands. Chirality plays a major role in nature, for example DNA double helix is a chiral right-handed structure. In magnetism, interactions between spins which are sensitive to chirality generate, in 2D structures with engineered interfaces, complex magnetic configurations as skyrmions that may be of future use in spintronics. In this study, researchers demonstrate the imprinting of complex 3D chirality at the nanoscale using state-of-the-art fabrication techniques and magnetic microscopy at MISTRAL. By fabricating a double helix ferromagnetic structure, magnetic domains were created having the same chirality of the double helix. Moreover, if the geometrical chirality was inverted in the course of the fabrication of the strand, then, the chirality of the magnetic domains was also inverted. At the location were both magnetic chiralities meet, a confined 3D magnetization was evidenced. The ability to create chiral 3D structures with nano patterning enables the control of complex topological magnetic states that might be important for future materials in which chirality provides a specific functionality.

Read more on the ALBA website

Image: Figure: a) 3D-printing of a cobalt nano-helix by FEBID. After injection of Co2(CO)8 into the chamber of a scanning electron microscope (SEM) using a gas injection system (GIS), the focused electron beam (in green and magenta) alternatively exposes the two helix strands. b) Coloured SEM image of the nanostructure under investigation, consisting of two double-helices of opposite chirality joined at the tendril perversion marked *. Scale bar 250nm, c) XMCD image of the double helix studied, which changes geometric chirality at *. Image at zero field, after application of a saturating field H along the axis as indicated. D) XMCD image of the double-helix under study in the as-grown state. Scale bars in c) and d) 200 nm.