Tunneling magnetoresistance effect in Co/TPD granular films

A series of Cox(TPD)1−x granular film samples were fabricated by co-evaporating technique, where Co nanoparticles are dispersed in TPD molecules matrix. The HRTEM images show typical microstructural characteristic of granular films. Magnetization, electrical conduction, and magnetoresistance (MR) of Cox(TPD)1−x granular films, have been investigated over a wide temperature range and Co volume fraction. The negative MR have been observed in these samples, reaching −1.75% (x = 36 vol.%, at 4.2 K, 10 kOe). The mechanism of magneto-transport behaviors has been discussed. It is suggested that the negative MR results from tunneling magnetoresistance (TMR) effect.