Intergranular coupling and activation volume of Co-Ni ferrite thin films with high coercivity above 3 kOe

Co-Ni ferrite film media with high coercivity above 3 kOe were fabricated b y ferrite plating and intergranular coupling and medium noise were discusse d. Increase of Co content in Co-Ni ferrite thin film with a thickness of 40 nm led to a decrease of intergranular exchange coupling and activation vol ume, resulting in the reduction of media noise in the high frequency region . The coercivity H-c increased with the Co content, and reached 3.6 kOe, At the maximum Co content, the activation volume took the minimum value of 6. 7x10(-18) cm(3), being smaller than the volume of a single grain in the fil m The medium noise was kept almost constant up to the linear recording dens ity of 144 kfrpi, while the noise of the media with the lower Co content an d lower H-c increased with the linear recording density.