Peculiar magnetism of Bi1−xDyxFeO3 ceramics at the morphotropic phase boundary

We report systematic studies on the crystal structure, optical phonons, and magnetic properties of Bi1−xDyxFeO3 (x = 0.1–0.2) systems at a morphotropic phase boundary (MPB) of R3c rhombohedral and Pnma orthorhombic structures. The structural phase coexistence is verified by observing two distinct X-ray diffraction profiles throughout the composition range. Rietveld refinement confirms the structural evolution from R3c to Pnma as the Dy concentration increases and provides details on the phase percentage and lattice parameters. Raman studies clearly reveal two different types of phonon vibrations in the coexisting phase. Weak ferromagnetism is observed in a composition with a dominant Pnma phase, meaning that the substitution of Dy weakly suppresses the cycloidal spin structure of the R3c phase. A pinched hysteresis loop is observed across the MPB and the magnetization reaches a maximum value and then decreases continuously as the Dy concentration increases. These observations are explained in the framework of the metamagnetic transition of antiferromagnetic clusters and the contribution of phase boundary spins.