Buffer-layer enhanced structural and electronic quality in ferrimagnetic Sr₂CrReO₆ epitaxial films

Highly ordered epitaxial Sr₂CrReO₆ films of 20-nm and 175-nm thicknesses were deposited on SrTiO₃ and (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.7 substrates and Sr₂CrNbO₆ buffer layers. Electronic measurements and scanning transmission electron microscopy images clearly show that the Sr₂CrNbO₆ buffer layers facilitate Cr/Re ordering near the interface, thus minimizing the number of defect states in the films. Arrhenius fits of the resistivity data give activation energies of 7.3–32 meV for films grown on non-buffered substrates, suggesting defect states are more conducting than Sr₂CrReO₆, whereas films grown on the Sr₂CrNbO₆ buffer layer have activation energies in the narrow range 38.6–42.1 meV.