The influence of Co doping on the dielectric, ferroelectric and ferromagnetic properties of Ba0.70Sr0.30TiO3 thin films

Ba0.70Sr0.30TiO3 (BST) thin films doped by Co (BSTC) are fabricated by sol-gel method on a Pt/Ti/SiO2/Si substrate. A strong correlation is observed among the microstructure, dielectric, ferroelectric, ferromagnetic properties and Co concentration. The dielectric constant of BST thin films can be tailored from 343 to 119 by manipulating the Co concentration. The dielectric loss of BSTC thin films are still kept below 0.020 and the tunability is above 30% at a dc-applied electric field of 500 kV/cm. With increasing Co doping up to 10 mol%, the coexistence of ferromagnetism and ferroelectrics is found. Suitable dielectric constant, low-dielectric loss, and high tunability of this kind of thin films can be useful for potential tunable applications.