Switching 2D Magnetic States via Pressure Tuning of Layer Stacking

The physical properties of two-dimensional van der Waals crystals can be sensitive to the interlayer coupling. For 2D magnets, theory suggests that the interlayer exchange coupling strongly depends on layer separation, while the stacking arrangement can even change the sign of the interlayer magnetic exchange, thus drastically modifying the ground state. Here, we demonstrate pressure tuning of magnetic order in the 2D magnet CrI₃. We probe the magnetic states using tunneling and scanning magnetic circular dichroism microscopy measurements. We find that the critical field for the spin-flip transition can be more than doubled by hydrostatic pressure. In bilayer CrI₃, pressure induces a transition from layered antiferromagnetic to ferromagnetic phases. In trilayer CrI₃, pressure can create coexisting domains of three phases, one ferromagnetic and two antiferromagnetic. The observed changes in magnetic order can be explained by changes in the stacking arrangement. Such coupling between stacking order and magnetism provides ample opportunities for designer magnetic phases and functionalities.