Low temperature ferromagnetism in perovskite SrIrO$_3$ films

TL;DR

This study reveals that epitaxial SrIrO₃ films exhibit low-temperature ferromagnetism and insulating behavior, contrasting with bulk properties, driven by lattice strain-induced structural distortions.

Contribution

It demonstrates that structural strain in SrIrO₃ films induces ferromagnetic ordering at low temperatures, highlighting the role of lattice distortions in tuning physical properties.

Findings

SrIrO₃ film shows ferromagnetism below 20 K

Electrical transport follows Mott's variable-range-hopping model

Positive magnetoresistance and anomalous Hall effect observed

Abstract

The 5$d$ based SrIrO$_3$ represents prototype example of nonmagnetic correlated metal which mainly originates from a combined effect of spin-orbit coupling, lattice dimensionality and crystal structure. Therefore, tuning of these parameters results in diverse physical properties in this material. Here, we study the structural, magnetic and electrical transport behavior in epitaxial SrIrO$_3$ film ($\sim$ 40 nm) grown on SrTiO$_3$ substrate. Opposed to bulk material, the SrIrO$_3$ film exhibits a ferromagnetic ordering at low temperature below $\sim$ 20 K. The electrical transport data indicate an insulating behavior where the nature of charge transport follows Mott's variable-range-hopping model. A positive magnetoresistance is recorded at 2 K which has correlation with magnetic moment. We further observe a nonlinear Hall effect at low temperature ($<$ 20 K) which arises due to an anomalous component of Hall effect. An anisotropic behavior of both magnetoresistance and Hall effect has been evidenced at low temperature which coupled with anomalous Hall effect indicate the development of ferromagnetic ordering. We believe that an enhanced (local) structural distortion caused by lattice strain at low temperatures induces ferromagnetic ordering, thus showing structural instability plays vital role to tune the physical properties in SrIrO$_3$.