STUDY OF CO - HFO2 GRANULAR FILMS DEPOSITED BY SEQUENTIAL SPUTTERING

Abstract

Granular films consist of single-domain magnetic nano-particles embedded in insulating matrix. This work explores a sequential sputtering technique for deposition of Co-HfO2 films to control the Co particle sizes and inter-particle distance. We showed that HfO2 insulator owing to its high binding energy could effectively decrease the formation of undesirable cobalt oxide in such films. Systematic compositional study on magneto-transport and magnetic properties, with individual control over Co and HfO2 components was performed. The magneto-transport properties exhibited tunnelling magnetoresistance (TMR) governed by charging energy. The Co-HfO2 films showed sizeable values of TMR ratio and high rate of change of TMR ratio with field. Post deposition annealing effects on such films were studied. The effects of inter-particle interactions among nano-particles were explored. The study highlighted on the difference between the physical and magnetic dimensions of nano-particles.