Crystalline phase dependent spin current efficiency in sputtered Ta thin films

We report on the optical detection of the spin Hall effect (SHE) as a function of the crystalline structure of sputtered Ta thin films using a magneto-optical Kerr system. The growth rate of Ta films is found to influence the crystalline phase of Ta films. At a lower growth rate, GR the pure α-phase of Ta is formed, which changes to the pure β-phase for GR ≥ 1.44 Å/s. For an intermediate growth rate, 0.62 Å/s ≤ GR