Existence of quasi-ferroelectricity in CoFe2O4 ferromagnetic films induced by Li+-Al3+ codopant

• Quasi-ferroelectric was induced by Li+-Al3+ co-dopant in CoFe2O4 thin film.
• The remanent polarization of Co0.9(Al0.5Li0.5)0.1Fe2O4 thin films was 5 μC/cm2.
• A new way for fabricating single phase multiferroic materials was provided.

Single phase multiferroics are rare in nature, because ferroelectric and ferromagnetic orderings require empty d-orbits and filled d-orbits, respectively. Here we demonstrate that ferroelectricity can be induced by ion-pair doping in ferromagnetic oxide such as ferrites with filled d-orbits. Our study shows that a new kind of room temperature multiferroic can be achieved in single phase thin films of CoFe2O4 with Li+-Al3+ pair substitution of Co2+ along 〈110〉 direction. A ferroelectric domain mechanism related to ion-pairs in co-doped thin films was revealed. Importantly, a new way for fabricating single phase multiferroic materials is provided in the present study.

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