Dissipative solitons have been reported in a wide range of nonlinear systems, but the observation of their magnetic analog has been experimentally challenging. Using spin transfer torque underneath a nanocontact on a magnetic thin film with perpendicular magnetic anisotropy (PMA), we have observed the generation of dissipative magnetic droplet solitons and report on their rich dynamical properties. Micromagnetic simulations identify a wide range of automodulation frequencies, including droplet oscillatory motion, droplet "spinning," and droplet "breather" states. The droplet can be controlled by using both current and magnetic fields and is expected to have applications in spintronics, magnonics, and PMA-based domain-wall devices.

Static and dynamic magnetic solitons play a critical role in applied nanomagnetism. Magnetic droplets, a type of non-topological dissipative soliton, can be nucleated and sustained in nanocontact spin-torque oscillators with perpendicular magnetic anisotropy free layers. Here, we perform a detailed experimental determination of the full droplet nucleation boundary in the current–field plane for a wide range of nanocontact sizes and demonstrate its excellent agreement with an analytical expression originating from a stability analysis. Our results reconcile recent contradicting reports of the field dependence of the droplet nucleation. Furthermore, our analytical model both highlights the relation between the fixed layer material and the droplet nucleation current magnitude, and provides an accurate method to experimentally determine the spin transfer torque asymmetry of each device.

Introduction oscillators (STOs) [4] are a novel class of microwave signal generators with an attractive set of properties, including a very large tuning range [5,6], a very high modulation rate [7][8][9], a small footprint [10], and the same compatibility with semiconductor technology as MRAM [11,12]. In addition, nanocontact-based STOs have recently been used as nanoscopic spin-wave injectors for magnonic applications [13]. While STO operation originally required very large external magnetic fields, recent innovation in combining materials with both in-plane (IP) and out-of-plane (OOP) anisotropy has made low to zero field operation possible [14][15][16], albeit with significant limitations in output power and frequency range. STOs with tilted anisotropies have been proposed to overcome these limitations [17,18], but while tilted anisotropy materials and spin valves (SVs) have already been developed [19][20][21], tilted STO operation has yet to be demonstrated. An alternative STO architecture