dear colleague

spin current can't be observed but you can evidence it by spin filtering using ferromagnetic material

regards

Dear Shalu Pathak,

an optical technique had been used, recently, to make direct measurements of the spin accumulation associated with the spin Hall effect.

Also, if an AC electrical technique (EIS[2]) technique is available, then you might be interested to measure some impedance spectra, using 4-classical[3] Hall contacts' topology, for different parametric values of the VDC polarizations[2,3]. The spin accumulation (at the edges) should have different time constant from other effects (grain boundary, etc.). In addition, if a magnet (for the common Hall effect) is available, then try to make a direct measurement for the classical Hall effect. The spin (Hall) accumulation at the edges should have different time constant (in AC electrical measurements) from the interfering (common/classical[3] , background quasi-DC) Hall effect.

1. Spin Hall effect is measured directly using light http://physicsworld.com/cws/article/news/2017/aug/31/spin-hall-effect-is-measured-directly-using-light

2. Basics of Electrochemical Impedance Spectroscopy https://www.gamry.com/application-notes/EIS/basics-of-electrochemical-impedance-spectroscopy/

3. Hall effect measurement setup : https://en.wikipedia.org/wiki/File:Hall_Effect_Measurement_Setup_for_Electrons.png (in https://en.wikipedia.org/wiki/Hall_effect)

Dear All, Thank you for your concern and giving an insight.

Dear Sir, I can understand that spin current can not observed directly (except the lase technique, which discovered recently). However researcher measure Quantum Spin Hall voltage, Spin Hall magneto-resistance etc. Then how they can measure it?

Dear Shalu Pathak,

for SMR what you have is really the combination of SHE and the inverse SHE (ISHE, the transformation by spin orbit interaction of spin current into a transversal charge current). In SMR, you have a NM layer ontop of a FM layer. You drive a charge current in the NM layer and, due to SHE, a spin current is produced. Depending on the orientation of the FM magnetization M, this spin current can be absorbed (M component parallel to the charge current) or reflected (M component perpendicular to the charge current). If it is reflected (totally or partically) at the interface, due to ISHE there will be a another charge current in the same direction that the original, and resistance will change.

ISHE is a common tool to measure spin currents.

Best regards,

Pilar