We have developed a magnetic scanning microscope operating at very low temperatures (0.2 kelvin). It is a well suited tool to detect magnetic fingerprints of topological superconductivity. We use a Superconducting Quantum interference Device (SQUID) as magnetic sensor in our microscope: Flying at a height of a few nanometers above the surface of the superconductor the SQUID probe intersects magnetic flux lines acquiring thus magnetic images. During the M2 internship the student will be familiarized with the cryogenic environment and scanning probe techniques before acquiring and interpreting magnetic images of superconductors with elements of the 5f family.

It has already been demonstrated that a large variety of synthetic langbeinites, based on the structure of K₂Mg₂(SO₄)₃, can be stabilized with room temperature non-centrosymmetric structures . Chemically speaking, fully substituting both sulfate SO42- for phosphate PO43- group and diamagnetic Mg2+ ions for paramagnetic Cr3+ cations is possible only if a mixed counter cation (Na+A2+) is introduced on the potassium site. NaBa1-xSrxCr2(PO4)3 solids, ceramics, with x=0 and 1 were recently reported to show intriguing physical properties (hysteric magneto capacitance signal when x=0 and a parallel magnetic long range ordering when x=1). During this internship we aim to grow single crystals NaBa1-xSrxCr2(PO4)3, from high temperature solutions, because obtaining single crystals is mandatory to investigate the physical properties/nuclear structure relationships with respect to an external stimulus. This work is developed in the frame of a collaboration project which main goal is the search of multiferroics solids based on polyanionic framworks.