Exploring new materials by high-pressure synthesis

Iron-based superconductors are a family of materials that attracts considerable attention, because of the high-temperature superconductivity and unconventional pairing mechanism. All compounds have a conducting layer made of iron and a pnictide (often Arsenic) and differ from the atoms and structure in between those layers. Among the different families, the Ca1−xLaxFeAs2, known as 112, is a recently discovered one. It also displays the peculiar property of having a conducting plane made of As zig-zag chains, as well as microscopic coexistence of superconductivity and antiferromagnetic order.

Using the high-pressure crystal growth apparatus in our laboratory, we created and investigated a new composition of 112 Fe-based superconductors, exploring the material properties when overdoped with electrons, achieved by replacing more than 50% Ca by La. Magnetic measurements show an antiferromagnetic transition at TN= 120 K, well above the one at lower doping (0.15 < x < 0.27). Because of the limited size of single crystals produced by high-pressure synthesis, Focused Ion Beam microstructure was used to prepare a hall bar sample for magnetoresistance and Hall coefficient measurement. To complete the study, single-crystal X-ray diffraction data have been collected at ESRF Synchrotron, further strengthening our findings from magnetization and transport measurements.