Coexistence of both magnetic ordering and ferroelectricity (with giant dielectric constant) have been observed for the first time in $\text{Co}{\left({\text{Fe}}_{1-x}{\text{Mo}}_x\right)}_2{\text{O}}_4$. The magnetization of $\text{Co}{\left({\text{Fe}}_{1-x}{\text{Mo}}_x\right)}_2{\text{O}}_4$ ($x$ ranges from 0 to 0.1) was found to increase with doping concentration of Mo. The magnetic properties indicate that Mo goes into the tetrahedral site. The giant dielectric constant may be attributed to the Maxwell-Wagner relaxation mechanism.

• Received 28 April 2010

DOI:https://doi.org/10.1103/PhysRevB.82.134428