Magnetic structures and phase transition of Ca2CoSi2O7

Recent advances in multiferroics, such as Ca2CoSi2O7, raise questions about their possible magnetic phases and transitions with temperature. In this article, we discuss all possible magnetic states and related structures of this compound on the basis of Density Functional Theory. The calculations were performed using different model supercells consisting of 1 to 4 unit cells. Different magnetic order states have been shown to transform into several basic structures whose population with temperature can clarify conflicting experimental data. The obtained probability of magnetic structures with temperature also explains the possible strong ferromagnetism, or weak paramagnetic response in the high field, and phase transition observed recently by acoustic phonon measurements. The competition between various magnetic ordering states shows why magnetization saturations were achieved only at high applied field and in low temperature region.