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The effect of Picosecond laser and Ultrafast Thermal magnetic
- Jun 10, 2016 -

The effect of Picosecond laser and Ultrafast Thermal magnetic

The rapid development of picosecond laser, for industrial processing adds a glimmer of hope. Recently, the University of Illinois at Urbana-Champaign scientists disclosed a new physical mechanism, scientists can use this physical mechanism to control the formation of magnetic heat. And a conventional field, the new mechanism relies on heat transfer, providing people with a new way to control the magnetization in the nanometer scale. Related papers published on a recent issue of "Nature Physics".

The researchers created a multi-layered metal spin valve structure comprising two magnetic layers and a heat transfer layer. "When the heat flow through the first layer of magnetic material, will produce electron spin separation. Our study is the use of it. With such a magnetic bipolar flow process, we can control the direction of the second magnetic layer." Champagne Professor of materials Science and Engineering Department David Cahill said.

"We use the ultrafast spin current is generated due to the thermal conductivity of spin transfer torque (STT). Spin Transfer Torque is transferred from a ferromagnetic conductive to the magnetization of spin angular momentum, so that people can spin current instead of magnetism to manipulate nano-magnets. "the school materials Science and Engineering Dr Chow said. Typically, the electric current generated by the magnetic layer to spin transfer torque, they now prove the existence of a mechanism to generate heat with a strong spin transfer torque, this mechanism is mainly driven by the Seebeck effect, the spin-dependent. Seebeck effect is a thermoelectric phenomenon, the same circuit a temperature difference between two different materials will produce a voltage. The spin Seebeck effect is dependent refers to a ferromagnetic spin electrons produced similar phenomena.

Metal spin valve structure, the researchers used a picosecond (trillionth of a second) laser pulses create a strong fast heat, heat transfer spin quantified. This heat per square meter 100GW (10 billion Watts), lasted about 50 picoseconds. "Symbolic and numerical heat-driven spin current can be controlled by the composition and thickness of the heat transfer layer of ferromagnetic layer." Cassirer said.

Nano devices spin, spin and heat coupling produces a new physical phenomenon, driven by the heat transfer Spin Transfer Torque to provide a new method of manipulating the local magnetization for people. Cassirer said: "The physical mechanism of the thermocouple effect with heat and thermal separation of the electron spin generators related to the heat generator to provide electricity to deep space probes in thermoelectric devices, heat causes charge separation, such a charge. separation can be used to detect the temperature, also be used to power. "