Structural, electrical and magnetic properties of granular Co_0.5 C_0.5 Films

Abstract

Structural, electrical and magnetic properties of granular Co _x C_{1- x} films are investigated, which have been prepared by electron-beam co-evaporation. The films consist of nanoscale Co-particles which are embedded within an amorphous C matrix. Post-deposition annealing and different substrate temperatures during evaporation were employed in order to reach different morphologies of the films. Two granular films with x = 0.5 are compared in detail, one of which was evaporated at a substrate temperature of T_S = 200°C. After deposition, the sample was subsequently annealed at T_a = 300°C and T_a = 350°C for 1 h each within an HV-furnace. The second sample was directly evaporated at a higher substrate temperature of T_S = 350° C. Significant changes are found in both their electrical and magnetic properties which are well explained as resulting from the slightly different morphologies of both films as obtained from TEM investigations.

Keywords:

• Co nanoparticles
• Magnetic coupling
• Magnetoresistance

Acknowledgements

One of us (H. W.) acknowledges support by the German Science Council (Graduate College “Structure and Dynamics of Heterogeneous Systems”).

Notes

¹Note that the MR was measured at T = 4.2 K, whereas the coercivity was determined for T = 300 K.