CaBaCo$_4$O$_7$ : A ferrimagnetic pyroelectric
  Magneto-electric coupling in pyroelectric CaBaCo$_4$O$_7$ is investigated using ab-intio calculations and Landau theory. The former shows that exchange-striction is strong enough to produce a giant change in electric polarization upon ferrimagnetic ordering, comparable to the experimentally determined value of ~17 mC/m$^2$ . Furthermore, Landau theory demonstrates that magneto-elastic coupling in CaBaCo$_4$O$_7$ is responsible for the strong magneto-electric coupling appearing close to the magnetic phase transition. 
R. D. Johnson, K. Cao, and P. G. Radaelli
cond-mat.str-el