Search for magnetochiral responses in curvilinear Geometries

• Applicant: Oleksii Volkov, Ph.D.
• Subject Area: Experimental Condensed Matter Physics ; Theoretical Condensed Matter Physics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 447482975

Investigations of magnetochiral responses in magnetism pave the way to novel concepts of magnonics, antiferromagnetic spintronics, spin-orbitronics and oxitronics. The main origin of these magnetochiral responses is associated with Dzyaloshinskii-Moriya interaction (DMI). This interaction arises in bulk magnetic crystals with a broken inversion symmetry or at the interfaces between a ferromagnet and nonmagnetic material with strong spin-orbit coupling. At present, tailoring of the DMI is done by optimizing materials, either doping bulk single crystals or adjusting interface properties of thin films and multilayers. In contrast to this, magnetochiral responses also appear in curvilinear geometries of conventional materials. A locally broken geometric symmetry leads to the restructuring of the exchange interaction in a way that appear two additional curvature-induced chiral and anisotropy interactions. Recently, we provided the very first experimental confirmation of the curvature-induced chiral interaction of exchange origin in a conventional soft ferromagnetic material. We determined the approach for the quantification of curvature-induced magnetochiral responses: measuring the depinning field of a domain wall from a curvilinear region enables one to quantify the strength of the curvature-induced DMI responses. With this paper, we have identified the pathway to study curvilinear effects in nanomagnets.Here, we aim to develop a fundamental quantitative and qualitative understanding of magnetochiral responses in curvilinear geometries relying on our experimental approach and recent theoretical predictions. To address this, we will fabricate (I) flat curvilinear stripes for the investigation of curvature-induced magnetochiral responses; (II) twisted three-dimensional stripes to study the torsion-induced effects; (III) corrugated films to quantify effects of principal curvatures. Technically, this project will rely on the comparison of pinning positions of magnetic textures with local geometrical parameters and measurements of depinning fields. In this prospective, it will be the first attempt to quantify (I) the stength of the torsion-induced DMI in twisted stripes; (II) magnetochiral responses summoned by principal curvatures in corrugated films, (III) the symmetry of the curvature-induced DMI for magnetic materials with in-plane and out-of-plane anisotropies. Thus, this project will provide the final missing link between theoretical predictions and experimental verifications in the field of curvilinear magnetism.

• DFG Programme: Research Grants