Structural, magnetic and dielectric properties in 3$d$-5$d$ based Sr$_2$FeIrO$_6$ thin films

TL;DR

This study investigates how strain and thickness affect the structural, magnetic, and dielectric properties of Sr$_2$FeIrO$_6$ thin films, revealing retained antiferromagnetic order and strain-dependent dielectric behavior.

Contribution

It provides new insights into the strain effects on multiferroic properties of 3$d$-5$d$ double perovskite thin films, with detailed spectroscopic and dielectric analysis.

Findings

Antiferromagnetic transition persists in films with shifted transition temperature.

Dielectric properties are closely related to magnetic ordering temperatures.

Strain influences dielectric constant, with higher values on LaAlO$_3$ substrates.

Abstract

The structural, magnetic and dielectric properties have been investigated in 3$d$-5$d$ based double perovskite Sr$_2$FeIrO$_6$ 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., SrTiO$_3$ (100) and LaAlO$_3$ (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 spectroscopy measurements indicate a Ir$^{5+}$ 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 ($\epsilon_r$) and loss ($\tan\delta$) show change around the magnetic ordering temperatures of bulk Sr$_2$FeIrO$_6$ 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., LaAlO$_3$ (100), the $\epsilon_r(T)$ and ($\tan\delta(T)$) show almost similar behavior but $\epsilon_r$ shows a higher value which is due to an increased strain coming from high mismatch of lattice parameters.