Bilayer

Quantum mechanics

Kerr effect

Magnetic field

Spin (aerodynamics)

Magnetization

Antiferromagnetism

Materials science

Ferromagnetism

Spin wave

Excitation

Biochemistry

Magnetism

Thermodynamics

Laser

Physics

Nonlinear system

Membrane

Optics

Terahertz radiation

Spin Hall effect

Condensed matter physics

Spin engineering

Chemistry

Magnonics

Electron

Magnetic anisotropy

Spintronics

Optoelectronics

Spin polarization

Ultrashort pulse

Nature Materials

The emergence of two-dimensional (2D) layered magnetic materials has opened an exciting playground for both fundamental studies of magnetism in 2D and explorations of spinbased applications. Remarkable properties, including spin filtering in magnetic tunnel junctions and gate control of magnetic states, have recently been demonstrated in 2D magnetic materials. While these studies focus on the static properties, dynamic magnetic properties such as excitation and control of spin waves have remained elusive. Here we excite spin waves and probe their dynamics in antiferromagnetic CrI3 bilayers by employing an ultrafast optical pump/magneto-optical Kerr probe technique. We identify sub-terahertz magnetic resonances under an in-plane magnetic field, from which we determine the anisotropy and interlayer exchange fields and the spin damping rates. We further show tuning of antiferromagnetic resonances by tens of gigahertz through electrostatic gating. Our results shed light on magnetic excitations and spin dynamics in 2D magnetic materials, and demonstrate their unique potential for applications in ultrafast data storage and processing.

Gate-tunable spin waves in antiferromagnetic atomic bilayers