Spin current generated by thermally driven ultrafast demagnetization

Abstract

Spin current is the key element for nanoscale spintronic devices. For ultrafast operation of such nano-devices, generation of spin current in picoseconds, a timescale that is difficult to achieve using electrical circuits, is highly desired. Here we show thermally driven ultrafast demagnetization of a perpendicular ferromagnet leads to spin accumulation in a normal metal and spin transfer torque in an in-plane ferromagnet. The data are well described by models of spin generation and transport based on differences and gradients of thermodynamic parameters. The temperature difference between electrons and magnons is the driving force for spin current generation by ultrafast demagnetization. On longer timescales, a few picoseconds following laser excitation, we also observe a small contribution to spin current by a temperature gradient and the spin-dependent Seebeck effect.

Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers

“…Nowadays, electrically generated spin currents are heavily used in the field of spintronics, where they are exploited to control the direction of the magnetization in a FM layer via the spin transfer torque (STT). A similar control of the magnetization on an ultrafast time scale can be established using an optically generated spin current, as was recently demonstrated using a noncollinear magnetic bilayer [14][15][16].…”

Laser-induced ultrafast spin current pulses: a thermodynamic approach

“…However, the Spin-Seebeck effect can be significant at interfaces as well as at lower electron gas temper atures [21,22,36]. Neglecting the Seebeck term, equation (5) simplifies to…”

“…If the injected spin direction is parallel or anti-parallel to the magnetization | | M 2 → is altered [19]. If there is an angle between M 2 → and the spin direction, the magnetization starts to precess [36,43].…”

Single shot ultrafast all optical magnetization switching of ferromagnetic Co/Pt multilayers

“…In a number of recent experiments [1][2][3][4][5][6][7][8] , it has been shown that femtosecond laser pulses can control magnetization on picosecond timescales, which is at least an order of magnitude faster compared to conventional magnetization dynamics. Among these demonstrations, the material system, GdFeCo ferrimagnetic films, is particularly interesting because deterministic toggleswitching of the magnetic order is possible without any external magnetic field.…”