Field-free spin-orbit torques switching and its applications

We review various approaches to field-free spin-orbit torque (SOT) switching. One approach involves introducing in-plane symmetric breaking methods to conventional SOT, such as an in-plane effective magnetic field or magnetic anisotropy, spatial non-uniformity, or a spin current density gradient. Another approach explores unconventional SOTs, which exploit out-of-plane spin polarization in low-symmetry materials or magnetic trilayer structures. Furthermore, we discuss the potential of field-free-SOT devices for various applications.