Multiferroic Materials and their Properties

Multiferroics, as the medium with more than one order parameter, have become a subject of great interest in the past decade. We present here a summary of the properties of a multiferroic, mostly a ferromagnet and a ferroelectric. They appear in three different forms; proper where the system is ferroelectric at high temperatures and becomes magnetic at low temperatures. These have weak magnetoelectric effects. Improper multiferroics undergo a transition to a magnetic as well as an electrically ordered state nearly concurrently. The electrical order can be ascribed to certain symmetry properties of the magnetic state. Finally, they can be prepared as solid mixtures. Our discussion is focused on the first two categories.