Magnetoresistivity of COBALT-PTFE granular composite film produced by pulsed laser deposition technique

Giant Magnetoresistance (GMR) was observed in Cobalt-PTFE heterogeneous granu- lar films. The samples were deposited on glass substrates by using the Pulsed Laser Deposition (PLD) technique. IR absorption spectra of the deposited PTFE showed similar characteristics with the bulk PTFE. The samples prepared exhibit a percentage change in resistance (MR%) of about 5% at room temperature with an applied magnetic field (H) of 10 kOe. A significant change of the MR profile was observed when the magnetic field was applied in-plane and out-of-plane to the film. The temperature dependence of resistance of the samples shows that charge transportation is mainly due to tunneling between the metal particles in the sample. The magnetization curve re- veals the superparamagnetic nature of the sample. The GMR effect can thus be interpreted by the spin-dependent electrons tunneling through the ferromagnetic metal granules (cobalt) in the insu- lating matrix (PTFE). An enhancement of MR% was observed at low temperature.