First and second principles study of magnetic and multiferroic properties of rare-earth orthoferrites

Rare-earth orthoferrite perovskites (RFeO3, where R is a rare-earth element, i.e., La, Gd, Dy, …) are a family of materials that have attracted a lot of attention due to their original magnetic properties and large nonlinear magnetoelectric responses (ME). A large magnetoelectric response will allow controlling magnetic properties using an electric field which can bring in a plethora of applications and improvements of the current technologies. In my thesis, I have studied magnetic properties of rare-earth orthiferrites and I have made a Heisenberg model to explain the origin of different unique magnetic behaviors (spin reorientation and magnetization reversal) present in these rare-earth orthoferrites. We have then used the model to explain large ME responses observed in these materials. We have shown that the nonlinear response present in these materials arises from the fact that the antiferromagnetic ordering changes nonlinearly with an applied magnetic field. Through a collaboration with experimentalists, we have also studied ultrafast manipulation of the magnetic phase of DyFeO3 using laser pulses in an ultrafast time scale which allows the use of these materials in memories with ultrafast time responses.