Magnetic properties, microstructures and magnetoresistance effect in Co/Alq3 granular films

A series of Cox(Alq3)1−x granular films were prepared using the co-evaporating technique. HRTEM images show typical characteristics of granular films with the average size of 2–5 nm. It shows a gradual change from superparamagnetism to ferromagnetism with the rise of x. Negative magnetoresistance (MR) was observed, reaching −5.31% in x=0.44 sample at 30 K under the field of 10 kOe. The concentration dependence of MR and resistivity is also investigated. The inter-particle tunneling is believed to account for the negative MR effect.