Planar-type spin valves based on low-molecular-weight organic materials with La0.67Sr0.33MnO3 electrodes

Abstract

The spin injection and transport properties of low-molecular-weight organic semiconductors such as pentacene and bis(l,2,5-thiadiazolo)-p-quinobis(l,3-dithiole) (BTQBT) were investigated utilizing planar-type spin-valve devices with half-metallic La0.67Sr0.33MnO3 electrodes. The devices showed clear spin-valve characteristics with a magnetoresistance (MR) ratio of up to 29% at 5K. The MR ratio was found to depend on the gap spacing of the electrodes, the applied bias voltage, temperature, and the crystallinity of the films. It was also affected by gas adsorption onto the films, indicating that the spins were scattered by carriers and/or radical ions in the films generated through charge transfer from gas molecules.

Spin-pump-induced spin transport in a thermally evaporated pentacene film

“…This is an advantage for the use of molecular materials in future applications of spintronics over the use of inorganic materials. To date, spin transport in pentacene films has been studied using a spin-polarized charge current, as distinct from pure spin current, has been studied, 5,6 although there is a conductance mismatch problem 13,14 between the ferromagnetic electrode as a spin injector and pentacene. This problem lowers the spin injection efficiency and produces errors in the estimation of spin transport…”

Spin current relaxation time in thermally evaporated pentacene films

“…3 Until now, the spin transport properties of some molecular materials have been investigated. [4][5][6][7][8][9] We have focused on pentacene molecular films prepared by thermal evaporation as one candidate material for the spin transport, in terms of the good crystallinity even in the thermally evaporated films, and the high electrical conductivity without any dopants. 10 Moreover, pentacene shows the photo-conductivity for visible light, 11 where the spin transport properties of pentacene can be controlled through visible light irradiation.…”

Pentacene thin films on ferromagnetic oxide: Growth mechanism and spintronic devices

“…12,18 After each step, the vacuum was broken for a couple of minutes to change the shadow masks. The pentacene films were deposited at room temperature in order to make the results comparable to those from the previous report on LSMO/pentacene spin valves 8 and to those obtained with other OSCs. 4,8,10,17,19 An AFM micrograph of the pentacene surface after the Al 2 O 3 deposition is reported in the left inset in Figure 1.…”

“…6 Despite this, its investigation in spintronics is limited to a very few cases. Spintronic effects at 5.3 K were reported for planar devices with La 0.7 Sr 0.3 MnO 3 (LSMO) electrodes and a pentacene spacer 8 (a spin diffusion length exceeding 200 nm was proposed in this paper) and in vertical devices comprising a Fe top electrode and a composite Co:TiO 2 bottom electrode separated by a 100 nm thick pentacene spacer. 9 On the other hand, no magnetoresistance (MR) effects were detected in pentacene-based devices fabricated without oxide electrodes, 10 unless oxidizing the pentacene layer in plasma oxygen.…”