The effect of A-site substitution of Ce and la on the magnetic and electronic properties of Sr(Ti_0.6Fe_0.4)O _3-δ films

The structure and magnetic properties of epitaxial (Ce_xSr _1-x)(Ti_0.6Fe_0.4)O_3-δ (x = 0, 0.1, 0.2 and 0.3) and (La_xSr_1-x)(Ti_0.6Fe _0.4)O_3-δ (x = 0, 0.1, 0.2, 0.3 and 0.4) perovskite-structure thin films deposited by pulsed laser deposition on (LaAlO₃)_0.3(Sr₂AlTaO₆) _0.7 (LSAT) substrates are reported. Both La and Ce ions showed a dominant 3+ valence state and acted as donors on the Sr²⁺ site (A site) in the perovskite lattice. The optical band gap widened, and the Fermi level moved toward the vacuum level with increased Ce or La content; meanwhile the Ti and particularly the Fe ions were driven to a lower valence state, resulting in a higher Fe²⁺ concentration. The materials were magnetic at room temperature with up to 0.8 μ_B/Fe and a magnetoelastic out-of-plane anisotropy. Ce and La lowered the coercivity while raising both the Faraday rotation at 1550 nm and the optical absorption at near-infrared wavelengths.