Enhanced magnetodielectric response in Dy modified NiCr2O4.

The chemically synthesized high purity spinel NiCr 2− x Dy x O 4 ( x = 0, 0.1) samples have been characterized using magnetic and dielectric measurements in presence of high magnetic field. Crystal and magnetic structure of the samples have been determined by analyzing neutron diffraction data recorded between temperature of 6 K and 300 K. NiCr 2 O 4 crystallizes in tetragonal phase with the space group of I 41/ amd whereas NiCr 1.9 Dy 0.1 O 4 crystallizes in the mixed phase of cubic (space group of Fd 3 ¯ m ) and tetragonal phases at room temperature. An additional phase of DyCrO 3 with orthorhombic structure has been found in the Dy doped compound. The lattice parameter a increases and the c decreases in tetragonal structure with the substitution of Dy in Cr site. Both the samples show superlattice reflection peak indicating the presence of long range AFM ordering (transverse component) below 40 K. But the saturation magnetization slightly increases after Dy doping. An anomaly observed near Curie temperature in ε ′ ( T ) of NiCr 2 O 4 and NiCr 1.9 Dy 0.1 O 4 demonstrates the contribution of coupling between ferroelectricity and ferrimagnetism in the compounds. A linear correlation between the difference in dielectric constant and the field dependent squared magnetization for both the samples has been observed. The spin–spin interactions are most likely responsible for the observed magnetodielectric (MD) effect due to the magnetodielectric hysteresis in both parent and doped samples. Interestingly the MD% is found to increase with Dy doping. [ABSTRACT FROM AUTHOR]