Landau Theory Description of Autferroicity

Autferroics, recently proposed as a sister branch of multiferroics, exhibit strong intrinsic magnetoelectricity, but ferroelectricity and magnetism are mutually exclusive rather than coexisting. Here, a general model is considered based on the Landau theory, to clarify the distinction between multiferroics and autferroics by qualitative change-rotation in a Landau free energy landscape and in particular phase mapping. The TiGeSe_{3} exemplifies a factual material, whose first-principles computed Landau coefficients predict its autferroicity. Our investigation paves the way for an alternative avenue in the pursuit of intrinsically strong magnetoelectrics.