Modification of magnetic properties, energy band gap and conduction mechanism of lanthanum orthochromite via (Sm, Fe) codoping

We report our investigations on the magnetic, thermal, optical and dielectric properties of the nanocrystalline La0.7Sm0.3Cr1−xFexO3 (0 ≤ x ≤ 0.3) samples synthesized through sol–gel auto-combustion process. The maximum magnetization and coercive field increase in Fe-doped samples. Fourier transform infrared (FTIR) spectra reveal the metal–oxygen (Cr/Fe–O) stretching and bending modes of vibration. Thermal analysis illustrates the occurrence of structural phase transition at ~ 290 °C for the pristine sample, and the phase transition temperature rises with the increase in Fe concentration. The specific heat capacity at constant pressure also reflects this transition. The energy band gap reduces for the doped samples. Dielectric constant, dielectric loss and loss tangent exhibit the usual frequency dependence and decrease with the amount of Fe. The Giuntini law implies higher contribution of polaronic conduction in the doped samples. Electric modulus analysis also shows the manifestation of both short- and long-range-order conduction processes in this system. The Nyquist plots for both impedance and electric modulus emphasize that grains dominate the conduction process. Temperature-dependent impedance and electric modulus analysis established that the relaxation processes are thermally activated and deviate from the ideal Debye behaviour.