GDCh Kolloquium - Professor Dr. Olivier Mentré

What layered iron compounds can offer, and more ...

I will introduce recently-found 2D inorganic compounds based on layers of Fe2+ (S=2) ions, in order to highlight how they form a unique platform for new paradigms on spin-dynamics and magneto-dielectric couplings. Here, depending on the crystal structure, the spin-degrees of freedoms and fine anionic compositions are the key-ingredients to tune the exchanges, crystal field ... etc. Especially, I will show in a specific 2D-Ising-ferromagnet (BaFe2(PO4)2) the occurrence of giant magneto-crystalline anisotropy. It results in the collective freezing of magnetic domains which mediates the passage from a soft to a ‘super-hard’ magnet. This unique situation offers various unexpected peculiarities including the ability to imprint any unreturnable magnetization to the sample within simple temperature/field cycles.