Structural, magnetic and dielectric properties in 3d–5d based Sr₂FeIrO₆ thin films

Abstract

The structural, magnetic and dielectric properties have been investigated in 3d–5d based double perovskite Sr2FeIrO6 thin films deposited by pulse laser deposition technique. To understand the effect of strain, epitaxial films are grown with varying thickness as well as on different substrates i.e., SrTiO3 (100) and LaAlO3 (100). The films with highest thickness are found to be more relaxed. Atomic force microscope images indicate all films are of good quality where grain sizes increase with increase in film thickness. X-ray absorption (XAS) spectroscopy measurements indicate a Ir5+ charge state in present films while providing a detailed picture of hybridization between Fe/Ir-d and O-p orbitals. The bulk antiferromagnetic transition is retained in films though the transition temperature shifts to higher temperature. Both dielectric constant (ϵ r) and loss (tan δ) show change around the magnetic ordering temperatures of bulk Sr2FeIrO6 indicating a close relation between dielectric and magnetic behaviors. A Maxwell–Wagner type relaxation is found to follow over whole frequency range down to low temperature in present film. On changing the substrate i.e., LaAlO3 (100), the ϵ r(T) and (tan δ(T)) show almost similar behavior but ϵ r shows a higher value which is due to an increased strain coming from high mismatch of lattice parameters.

Low temperature ferromagnetism in perovskite SrIrO$_3$ films

“…In case of iridium, the Ir-L 3 absorption edge has usually been seen to occur at 11218.0, 11219.6, 11220.0, 11222.0 and 11222.5 eV for Ir, Ir 3+ , Ir 4+ , Ir 5+ and Ir 6+ charge state, respectively. [32][33][34][35][36][37] Given that the absorption edge is very sensitive to local environment of anions, a small difference in energy position may occur from system to system. The L 3 edge at 11219.95(4) eV in present film suggests iridium is in Ir 4+ state.…”