Field-free switching of perpendicular magnetization in an ultrathin epitaxial magnetic insulator

Abstract: For energy efficient and fast magnetic memories, switching of perpendicular magnetization by the spin-orbit torque (SOT) appears as a very promising solution, even more using magnetic insulators that suppress electrical shunting. This SOT switching generally requires the assistance of an in-plane magnetic field to break the symmetry. Here, we present experiments demonstrating the field-free SOT switching of perpendicularly magnetized layers of the thulium iron garnet (Tm_{3}Fe_{5}O_{12}) magnetic insulator. The polarity of the switching loops, clockwise (CW) or counter-clockwise (CCW), is determined by the direction of the initial current pulses, in contrast with field-assisted switchings in which this polarity is controlled by the direction of the field. After an independent determination of Dzyaloshinskii-Moriya interaction (DMI), we relate the field free switching to the interplay of SOT and DMI and the polarity of the loops to the imprint of a N\'eel domain wall induced by the first pulse, in agreement with Kerr imaging. Our observation and interpretation of field-free electrical switching of a magnetic insulator is an important milestone for future low power spintronic devices.