The UC Riverside-led research is said to be significant because it demonstrates that a tri-layer, sandwich-like, structure can serves as a scalable pure spin current device, an essential ingredient in spintronics.
A key element in this breakthrough is the material. To demonstrate the effect, the magnetic insulator needs to be truly insulating, or there will be a parasitic signal from leakage. On the other hand, a high-quality magnetic insulator grown on metal had never been demonstrated.
Jing Shi, professor of physics at the University of California, Riverside, said: "Using a combination of sputtering and pulsed laser deposition, we showed that the 50 to 100nm thick magnetic insulator, in this case yttrium iron garnet, is not only magnetic and insulating, but also of high quality when it is grown on 5nm thick platinum."
In the structures used by the researchers, there are two metals and a magnetic insulator in between. The metals are for spin current generation and detection via the spin Hall effect and inverse spin Hall effect.
The magnetic insulator is an electrical insulator but a good spin current conductor. The spin current flowing in the insulator does not involve mobile electrons therefore it does not dissipate energy as an electrical current does in joule heating.
The researchers also claim to have demonstrated that the signal transmission can be switched on and off and modulated in its strength by a magnetic field. The electrical signal transmission through the magnetic insulators can be switched on and off depending on the magnetic state, or direction of the magnetisation, of the magnetic insulators.
This means that the direction of the magnetisation can be regarded as a memory state of non-volatile random access memory devices. In addition, the signal level can be modulated by changing the direction of the magnetisation; suiting it for use in analogue devices. The researchers also say that sandwich structure can be scaled down with nanofabrication.
