Structural, electronic and magnetic properties of the series of double perovskites (Ca,Sr)2−xLaxFeIrO6(Ca,Sr)2−xLaxFeIrO6

• The double perovskite series (Ca,Sr)2−xLaxFeIrO6(Ca,Sr)2−xLaxFeIrO6 were synthesized.
• Changes in the Fe-Ir magnetic coupling due to La doping on both series.
• Evidence of high TCTC on Sr1.2La0.8FeIrO6Sr1.2La0.8FeIrO6.
• Indication of Mott insulator behavior on Sr2FeIrO6Sr2FeIrO6.

Polycrystalline samples of the series of double perovskites Sr2−xLaxFeIrO6Sr2−xLaxFeIrO6 were synthesized. Their structural, electronic and magnetic properties were investigated by X-ray powder diffraction, Mössbauer spectroscopy, magnetic susceptibility, heat capacity and electrical resistivity experiments. The compounds crystallize in a monoclinic structure and were fitted in space group P21/nP21/n, with a significant degree of Fe/Ir cationic disorder. As in Ca2−xLaxFeIrO6Ca2−xLaxFeIrO6 the Sr-based system seems to evolve from an antiferromagnetic ground state for the end members (x=0.0 and x  =2.0) to a ferrimagnetic order in the intermediate regions (x~1x~1). Since Mössbauer spectra indicate that Fe valence remains 3+ with doping, this tendency of change in the nature of the microscopic interaction could be attributed to Ir valence changes, induced by La3+ electrical doping. Upon comparing both Ca and Sr series, Sr2−xLaxFeIrO6Sr2−xLaxFeIrO6 is more structurally homogenous and presents higher magnetization and transition temperatures. Magnetic susceptibility measurements at high temperatures on Sr1.2La0.8FeIrO6Sr1.2La0.8FeIrO6 indicate a very high ferrimagnetic Curie temperature TC~700K. For the Sr2FeIrO6 compound, electrical resistivity experiments under applied pressure suggest that this material might be a Mott insulator.

The Weiss constant as a function of La doping for the (Ca,Sr)2−xLaxFeIrO6(Ca,Sr)2−xLaxFeIrO6 series, indicating changes in Fe–Ir magnetic coupling on both families.Figure optionsDownload as PowerPoint slide