Valley-Related Multipiezo Effect and Noncollinear Spin Current in an Altermagnet Fe 2 Se 2 O 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 Fe 2 Se 2 O 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 Fe 2 Se 2 O monolayer reaches 860 meV. Moreover, an Fe 2 Se 2 O 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 Fe 2 Se 2 O 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 Fe 2 Se 2 O monolayer doped with 0.2 hole/formula unit. These excellent physical properties make the Fe 2 Se 2 O monolayer a promising candidate for multifunctional spintronic and valleytronic devices.