A. Einstein and W.J. de Haas discovered experimentally the equivalence of magnetic moment and mechanical rotation in 1915 [1].
In the same year, S.J. Bernett showed that the mechanical rotation can generate a magnetic field, i.e., the so-called Bernett field, even in a body with no electric charge [2].
These phenomena are caused by the angular momentum conservation between electron spin and mechanical rotation, which has been proved in the general relativistic quantum mechanics [3].
We introduce mechanical effects in spintronics and propose a variety of novel spintronics phenomena. In particular, the coupling between nuclear spin and mechanical rotation is demonstrated [4]. Since the Bernett field is enhanced more than three orders of magnitudes in nuclei than electron spins, the mechanical nuclear-magnetic-resonance (NMR) may provide new applications of NMR.
We also observe the generation of spin current by the flow of liquid metals. Combining this effect with the spin Hall effect [5], the spin-hydrodynamic generation of electricity is obtained [6].
The mechanical generation of spin and spin current opens a door from “Spintronics” to “Spin-Mechatronics”.

 

[1] A.Einstein and W.J.de Haas, Verhandl.Deut.Physik.Ges, 17,154 (1915).
[2] S.J.Bernett, Phys. Rev. 6, 239 (1915).
[3] M.Matuo, J.Ieda and S.Maekawa, Phys. Rev. Lett. 106, 076601 (2011).
[4] H.Chudo,M.Ono, K.Harii, M.Matsuo, J.Ieda, R.Haruki,S.Okayasu, S.Maekawa, H.Yasuoka and E.Saitoh, Appl. Phys. Express 7, 063004 (2014).
[5] Spin Current, eds. S. Maekawa et al. (Oxford University Press, 2012).
[6] R.Takahashi, M.Ono, K.Harii, S.Okayasu, M.Matsuo, J.Ieda, S.Takahashi, S.Maekawa and E.Saitoh, Nature Phys. 12, 52 (2016).