Spin current relaxation time in thermally evaporated pentacene films

The spin current relaxation time [tau] in thermally evaporated pentacene films was evaluated with the spin-pump-induced spin transport properties and the charge current transport properties in pentacene films. Under an assumption of a diffusive transport of the spin current in pentacene films, the zero-field mobility and the diffusion constant of holes in pentacene films were experimentally obtained to be ~8.0x10^-7 m^2/Vs and ~2.0x10^-8 m^2/s, respectively. Using those values and the previously obtained spin diffusion length in pentacene films of 42{plus-minus}10 nm, the [tau] in pentacene films was estimated to be 150{plus-minus}120 ns at room temperature. This estimated [tau] in pentacene films is long enough for practical use as a spintronic material.