Designing new type of multiferroics with altermagnets

We introduce a new class of materials termed multiferroic altermagnets, which exhibit a novel coupling between ferroelectric polarization and altermagnetic energy splitting between spin channels. By synergistically linking the switch of ferroelectric polarization with altermagnetic properties, we demonstrate an approach to control spin dynamics via electric polarization. Leveraging advanced spin-group symmetry techniques, we establish fundamental symmetry-based criteria for identifying and manipulating altermagnetic spin splitting in response to changes in electric polarization.

A systematic screening of 2,001 experimentally reported magnetic structures in the MAGNDATA database reveals 22 promising ferroelectric altermagnets, of which two are confirmed to be multiferroic altermagnets. We showcase the tight coupling between altermagnetic spin splitting and ferroelectric polarization, establishing it as an ideal prototype for designing multiferroic devices.

Furthermore, we discuss how this coupling enables experimental detection through monitoring physical quantities linked to the non-vanishing Berry curvature dipole, such as linearly polarized photogalvanic spin currents. Our findings present a robust framework for exploring and realizing novel multiferroic devices, opening avenues for future research in functional spintronics.