Synthesis and Magnetic Properties of the Multiferroic [C(NH 2 ) 3 ]Cr(HCOO) 3 Metal-Organic Framework: The Role of Spin-Orbit Coupling and Jahn-Teller Distortions.

We report for the first time the synthesis of [C(NH 2 ) 3 ]Cr(HCOO) 3 stabilizing Cr 2+ in formate perovskite, which adopts a polar structure and orders magnetically below 8 K. We discuss in detail the magnetic properties and their coupling to the crystal structure based on first-principles calculations, symmetry, and model Hamiltonian analysis. We establish a general model for the orbital magnetic moment of [C(NH 2 ) 3 ]M(HCOO) 3 (M = Cr, Cu) based on perturbation theory, revealing the key role of the Jahn-Teller distortions. We also analyze their spin and orbital textures in k -space, which show unique characteristics.