Istvan Kezsmarki (University of Augsburg) Magnetic avalanche of non-oxide conductive domain walls
Conductive domain walls have been exclusively observed in oxides, where off-stoichiometry and defects often hamper the domain wall conductivity and render the walls immobile and thus curtail their usefulness and flexibility. In this talk, we will show the giant conductivity of domain walls in the non-oxide multiferroic GaV4S8, investigated by macroscopic transport as well as scanning probe microscopy experiments [1]. We observe fascinating architectures of ribbon- and folded sheet-like conductive domain walls emerging in the polar rhombohedral state of GaV4S8 below its Jahn-Teller transition at TJT = 45 K. Besides the giant negative magnetoresistance inherent to these conductive domain walls, their high conductivity is exploited to trigger unprecedentedly large changes of the bulk resistance via on-demand magnetic or electric conversions between multi- and mono-domain states. Such a transformation to the insulating mono-domain state through an avalanche-like domain-wall expulsion process leads to an abrupt conductance changes as large as eight orders of magnitude. These unique properties demonstrate that non-oxide ferro-electrics can be the source of novel phenomena beyond the realm of oxide electronics. The enhanced conduction of the domain walls originates from local strain [2], which may induce an insulator-to-metal transition at those interfaces. Taking advantage of the strain effect, we demonstrate that nanoscale conductive lines can be created artificially in this system.
[1] S. Ghara et al., Nat. Commun. 12, 3975 (2021)
[2] L. Puntigam et al., Adv. Electron.Mater. 8, 2200366 (2022)