Giant Faraday rotation of cobalt ferrite thin films deposited on silicon substrates for silicon photonic nonreciprocal device applications

Abstract

In this study, crystalline cobalt ferrite thin films with large Faraday rotation (FR) coefficient were deposited on silicon by radiofrequency magnetron sputtering. An (100)-oriented MgO buffer layer was employed to solve the film/substrate discrepancy. A giant FR coefficient of 25 600 deg cm−1 was achieved for a cobalt ferrite film deposited at a substrate temperature (ST) of 600 °C. Moreover, the magnetic easy axis of the films switched from in-plane (IP) to out-of-plane orientation with increasing ST. This switching in the easy axis could be attributed to induced IP stress in the films with high deposition temperatures.