Science Daily  October 18, 2023
Multiferroics have multifunctional electrical and magnetic device applications. Two-dimensional materials with honeycomb lattices offer opportunities to engineer unconventional multiferroicity. Orbital multiferroics could offer strong valley–magnetic couplings and large responses to external fields—enabling device applications such as multiple-state memory elements and electric control of the valley and magnetic states. An international team of researchers (USA – MIT, Harvard University, Japan) has shown orbital multiferroicity in Penta layer rhombohedral graphene. They observed anomalous Hall signals Rxy with an exceptionally large Hall angle and orbital magnetic hysteresis at hole doping. There were four such states with different valley polarizations and orbital magnetizations, forming a valley–magnetic quartet connected by a butterfly-shaped hysteresis of Rxy. Tuning E would switch each ferroic order independently and achieve non-volatile switching of them together. According to the researchers their observations demonstrate a previously unknown type of multiferroics and point to electrically tunable ultralow-power valleytronic and magnetic devices… read more. TECHNICAL ARTICLE
Gate-induced Berry curvature and valley–magnetic quartet… Credit: Nature, 18 October 2023Â