Abstract:
Herein, a comprehensive investigation into the effect of alkaline-earth hole doping on the structural, thermal, and electronic properties of Dy0.6A0.4MnO3 (A = Ca, Sr, and Ba) multiferroics is reported. Room-temperature X-ray diffraction confirms that all samples retain the orthorhombic perovskite structure (Pbnm), with subtle lattice distortions induced by ion substitution. Thermal analyses show that Sr doping exhibits an anomalous mass loss of 4.8% between 100 and 1000 degrees C along with a reduced crystallization enthalpy (0.43 J g-1) relative to the Ca and Ba-substituted compounds. Phase-field simulations, based on a classical double-well potential coupled with a gradient energy term, capture the evolution of crystalline domains and yield crystallization enthalpies which validate the experimental trend. Hard X-ray photoelectron spectroscopy confirms the coexistence of mixed Mn3+/Mn4+ states, effecting a partial transformation of Jahn-Teller active Mn3+ ions into non-Jahn-Teller Mn4+ ions while zeta potential measurements reveal surface charges of 22.2 (Ca), 16.1 (Sr), and 21.4 mV (Ba), reflecting differences in colloidal stability. These results demonstrate that Sr substitution engenders a unique stabilization mechanism, likely due to the coordination mismatch between the small eightfold coordinated Dy3+ and the slightly larger 12-fold coordinated Sr2+, thereby offering a tunable route for optimizing the multifunctional properties of multiferroic oxides.
