  We report spin amplification using a capacitive beam splitter in n-type GaAs
where the spin polarization is monitored via transverse electron focusing
measurement. It is shown that partially spin-polarized current injected by the
emitter can be precisely controlled and the spin polarization associated with
it can be amplified by the beam splitter, such that a considerably high spin
polarization of around 50% can be obtained. Additionally, the spin remains
coherent as shown by the observation of quantum interference. Our results
illustrate that spin polarization amplification can be achieved in materials
without strong spin-orbit interaction.
