  The high Curie temperature multiferroic compound, CuO, has a quasidegenerate
magnetic ground state that makes it prone to manipulation by the so called
``order-by-disorder'' mechanism. First principle computations supplemented with
Monte Carlo simulations and experiments show that isovalent doping allows to
stabilize the multiferroic phase in non-ferroelectric regions of the pristine
material phase-diagram with experiments reaching a 250% widening of the
ferroelectric temperature window with 5% of Zn doping. Our results allow to
validate the importance of a quasidegenerate ground state on promoting
multiferroicity on CuO at high temperatures and open a path to the material
engineering of new multiferroic materials.
