Structural, magnetic, dielectric and magnetodielectric properties of Bi_{1− x} Ca _x Fe_{1− x} Mn _x O₃ in the morphotropic phase boundary region

Structural, magnetic, dielectric and magnetodielectric properties of Ca and Mn co-substituted bismuth ferrite, Bi_{1− x} Ca _x Fe_{1− x} Mn _x O₃ (0  ⩽   x   ⩽  0.4) are reported. Structural studies by Rietveld refinement of XRD patterns revealed rhombohedral R3c structure for x   ⩽  0.11 and orthorhombic Pbnm structure for x   ⩾  0.2. For compositions in the range 0.11  <   x   <  0.2, mixed phase behaviour is observed showing a morphotropic phase boundary (MPB) region. Magnetisation at room temperature increases with increasing Ca and Mn content, showing weak ferromagnetism. Coercivity and remanence initially increase and then decrease with increasing x , showing a maximum for x   =  0.175 in the MPB region. Dielectric constant also shows a maximum value in the mixed phase region. Magnetodielectric (MD) studies revealed positive MD for the R3c phase and a negative MD for the Pbnm phase, showing a maximum MD (∼1%) for x   ≈  0.1 and crossover at x   ≈  0.175. The studies show strong interplay between the structure and properties, suggesting tuneable bismuth ferrite based compositions for magnetoelectric applications. (paper)