Transition from the macrospin to chaotic behavior by a spin-torque driven magnetization precession of a square nanoelement

We demonstrate (using full-scale micromagnetic simulations) that the spin-injection driven steady-state precession of a thin magnetic nanoelement exhibits a complicated transition from a quasimacrospin to chaotic behavior with increasing element size. For nanoelement parameters and magnetic fields typical of those used experimentally we show that the macrospin approximation is invalid already for very small nanoelement sizes (similar to 30 nm).