All-optical subnanosecond coherent spin switching in thin ferromagnetic layers

Abstract

The need for faster magnetic recording devices has driven researchers to seek more efficient ways to reverse the magnetization. A large variety of methods and materials has been investigated to accomplish the most rapid spin reorientation, ranging from magnetic field pulses in ferromagnetic compounds to ultrashort optical excitations in ferrimagnetic and antiferromagnetic materials. To date, the precessional motion in an external field is the most effective route to control the magnetization in ferromagnets. Reversible switching under simple experimental conditions, i.e., in air and at room temperature, with a moderate optical excitation is a goal that has not been reached so far. Here we demonstrate that, using short laser pulses, the magnetization of a thin biaxial ferromagnetic layer can be optically and repeatedly commuted between well-defined directions on a time scale of 100 ps.