Remarkable effects of dopant valency - a comparative study of CaBaCo3.96Cr0.04O7 and CaBaCo3.96Ni0.04O7

Distinctive effects of dopant valency is discussed using an impurity level 1% doping each of Cr3+ and Ni2+ in CaBaCo4O7. Through a comparative study of the magnetic and dielectric properties of magnetoelectric CaBaCo3.96Cr0.04O7 and CaBaCo3.96Ni0.04O7, we highlight that Cr doping does not significantly alter the properties in spite of differences in magnetic spin and ionic radius compared to Co3+ and Co2+ while Ni doping induces spectacular changes. Particularly, about 4 times larger electric polarization change (similar to 650 mu C/m(2) at 5.6 kV/cm) is observed in CaBaCo3.96Ni0.04O7 compared to CaBaCo3.96Cr0.04O7 and a stronger magnetoelectric coupling leading to a polarization change of similar to 12% in 15 T magnetic field, below 40 K. Further, magnetodielectric effects hint to competing magnetic phases over the temperature range of magnetic transitions. The article discusses the observed disparity in the light of a possible site selective doping of Cr3+ and Ni2+ in the triangular and kagome layers, respectively, of the parent compound.