Valley-Related Multipiezo Effect and Noncollinear Spin Current in an Altermagnet Fe₂Se₂O Monolayer

An altermagnet exhibits many novel physical phenomena because of its intrinsic antiferromagnetic coupling and natural band spin splitting, which are expected to give rise to new types of magnetic electronic components. In this study, an Fe₂Se₂O monolayer is proven to be an altermagnet with out-of-plane magnetic anisotropy, and its Néel temperature is determined to be 319 K. The spin splitting of the Fe₂Se₂O monolayer reaches 860 meV. Moreover, an Fe₂Se₂O monolayer presents a pair of energy valleys, which can be polarized and reversed by applying uniaxial strains along different directions, resulting in a piezovalley effect. Under the strain, the net magnetization can be induced in the Fe₂Se₂O monolayer by doping with holes, thereby realizing a piezomagnetic property. Interestingly, noncollinear spin current can be generated by applying an in-plane electric field on an unstrained Fe₂Se₂O monolayer doped with 0.2 hole/formula unit. These excellent physical properties make the Fe₂Se₂O monolayer a promising candidate for multifunctional spintronic and valleytronic devices.