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Register a new userStructural properties and anisotropic electronic transport in SrIrO3 films
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Perovskite SrIrO3 (SIO) films epitaxially deposited with a thickness of about 60 nm on various substrate materials display nearly strain-relieved state. Films grown on orthorhombic (110) DyScO3 (DSO) are found to display untwinned bulk-like orthorhombic structure. However, film deposition on cubic (001) SrTiO3 induces a twinned growth of SIO. Resistance measurements on the SIO films reveal only weak temperature dependence, where the resistance R increases with decreasing temperature T. Hall measurements show dominant electron-like transport throughout the temperature range from 2 K to 300 K. At 2 K, the electron concentration and resistivity for SIO on STO amount to ne = 1.4*10^20 cm-3 and 1 mohmcm. Interestingly, the film resistance of untwinned SIO on DSO along the [1-10] and the [001] direction differs by up to 25% indicating pronounced anisotropic electronic transport. The anisotropy of the resistance increases with decreasing T and displays a distinct maximum around 86 K. The specific T-dependence is similar to that of the structural anisotropy sqrt(a2+b2)/c of bulk SIO. Therefore, anisotropic electronic transport in SIO is very likely induced by the orthorhombic distortion. Consequently, for twinned SIO films on STO anisotropy vanishes nearly completely. The experimental results show that structural changes are very likely responsible for the observed anisotropic electronic transport. The strong sensitivity of the electronic transport in SIO films may be explained in terms of the narrow electron-like bands in SIO caused by spin-orbit-coupling and orthorhombic distortion.
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Epitaxial perovskite (110) oriented SrIrO3 (SIO) thin films were grown by pulsed laser deposition on (110) oriented DyScO3 (DSO) substrates with various film thickness t (2 nm < t < 50 nm). All the films were produced with stoichiometric composition, orthorhombic phase, and with high crystallinity. The nearly perfect in-plane lattice matching of DSO with respect to SIO and same symmetry result in a full epitaxial inplane alignment, i.e., the c-axis of DSO and SIO are parallel to each other with only slightly enlarged d110 out-of-plane lattice spacing (+0.38%) due to the small in-plane compressive strain caused by the DSO substrate. Measurements of the magnetoresistance MR were carried out for current flow along the [001] and [1-10] direction of SIO and magnetic field perpendicular to the film plane. MR appears to be distinctly different for both directions. The anisotropy MR001/MR1-10 > 1 increases with decreasing T and is especially pronounced for the thinnest films, which likewise display a hysteretic field dependence below T* ~ 3 K. The coercive field Hc amounts to 2-5 T. Both, T* and Hc are very similar to the magnetic ordering temperature and coercivity of DSO which strongly suggests substrate-induced mechanism as a reason for the anisotropic magnetotransport in the SIO films.
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