Remarkable effects of dopant valency $-$ a comparative study of CaBaCo${}_{3.96}$Cr${}_{0.04}$O${}_7$ and CaBaCo${}_{3.96}$Ni${}_{0.04}$O${}_7$

Abstract

Distinctive effects of dopant valency is discussed using an impurity level 1% doping each of Cr${}^{3+}$ and Ni${}^{2+}$ in CaBaCo${}_4$O${}_7$. Through a comparative study of the magnetic and dielectric properties of multiferroic CaBaCo${}_{3.96}$Cr${}_{0.04}$O${}_7$ and CaBaCo${}_{3.96}$Ni${}_{0.04}$O${}_7$, we highlight that Cr doping does not significantly alter the properties in spite of differences in magnetic spin and ionic radius compared to Co${}^{3+}$ and Co${}^{2+}$ while Ni doping induces spectacular changes. Particularly, a manifold increase of electric polarization change up to 650 $\hat{\mathrm{I}}¼$C/m${}^2$ at 5.6 kV/cm is observed in CaBaCo${}_{3.96}$Ni${}_{0.04}$O${}_7$ compared to CaBaCo${}_{3.96}$Cr${}_{0.04}$O${}_7$ and a stronger magnetoelectric coupling leading to a polarization change of $\sim$ 12% in 15 T magnetic field and below 40 K. Further, magnetodielectric effects hint to competing magnetic phases over the temperature range of magnetic transitions. We discuss the observed disparity in the light of a possible site selective doping of Cr${}^{3+}$ and Ni${}^{2+}$ in the triangular and kagomé layers, respectively, of the parent compound.

7 pages, 4 figures, 3 tables