Magneto-optical detection of spin accumulation under the influence of mechanical rotation

Abstract

The generation of spin-polarised carriers in a non-magnetic material holds the key to realise highly efficient spintronic devices. Recently, it has been shown that the large spin-orbit coupling can generate spin-polarised currents in noble metals such as tungsten and platinum. Especially, if small samples of such metals are rotated on a plane disc in the presence of a perpendicular magnetic field, the orbital angular momentum is altered leading to a segregation of spin up and spin down electrons, i.e., a spin current in the samples. This is manifested via an induced magnetic moment on the metal. In this letter, magneto-optical Kerr effect (MOKE) is used to detect induced magnetic moments which allows remote measurements on metal samples rotating at 100~210 Hz. Our results confirm the mechanical generation of spin-polarised currents via optical detection of spin accumulation.

Gyromagnetic bifurcation in a levitated ferromagnetic particle

“…Originally, gyromagnetic effects were investigated in bulk magnetic materials with aim of determining their gyromagnetic ratios [3]. Recently, gyromagnetic effects have been recognized as universal phenomena, as demonstrated in various systems at scales ranging from those of condensed matter [4][5][6][7][8][9][10][11][12][13][14][15][16] to those of particle physics [17][18][19][20][21]. They have also provided powerful tools with which to measure and control both the mechanical and magnetic degrees of freedom [4,5,[22][23][24][25][26][27].…”

“…Indeed, the Barnett effect (conversion of angular momentum of mechanical rotation into spin [1]) has been utilized to identify the angular momentum compensation temperature of ferrimagnets [24,25] and to generate spin current from rigid-body rotation [6][7][8], surface acoustic waves [13][14][15], and vorticity in fluids [9][10][11][12]. On the other hand, the Einstein-de Haas effect (mechanical torque generated from spin polarization [2]) has been utilized to measure the faint torque caused by a single electron spin flip [23], identify the gyromagnetic ratio of a nanomagnetic thin film [22], and reveal the demagnetization process in ferromagnets on sub-picosecond time scales [26].…”

Eddy magnetization from the chiral Barnett effect

“…Interestingly, the theoretical predictions have been experimentally confirmed recently, see Refs. [20][21][22]. For more details, interested readers can consult a recent textbook [23].…”

Determination of spin relaxation time and spin diffusion length by oscillation of spin pumping signal

“…Recent topics in spintronics are mostly concerned with generation and detection of spin. A variety of methods of the generating spin accumulation and spin current have been investigated in the past few decades, such as the spin pumping effect [1][2][3] , spin Hall effect [4][5][6][7][8][9] , spin Seebeck effect [10][11][12][13] , gyromagnetic effect [14][15][16][17][18] and nonlocal spin-valve devices 19 . The generated spin is detected by using reciprocal phenomena of the generation, such as the inverse spin Hall effect 8,20,21 , ac spin current detection by spin-transfer torque ferromagnetic resonance 22 , and also detected optically 18,[23][24][25][26] .…”