  Multiferroics offer exciting opportunities for electric-field control of
magnetism. Unfortunately, single-phase multiferroics suitable for such
applications at room temperature has not been discovered. Here, we propose the
concept of a new type of multiferroics, namely, "asymmetric multiferroic". In
asymmetric multiferroics, two locally stable ferroelectric states are not
symmetrically equivalent, leading to different magnetic properties between
these two states. Furthermore, we predict from first-principles that a Fe-Cr-Mo
superlattice with the LiNbO3-type structure is such an asymmetric multiferroic.
The strong ferrimagnetism, high ferroelectric polarization, and significant
dependence of the magnetic transition temperature on polarization make this
asymmetric multiferroic an ideal candidate for realizing electric-field control
of magnetism at room temperature. Our study suggests that asymmetric
multiferroic may provide a new playground for voltage control of magnetism and
find its applications in spintronics and quantum computing.
