Competition between compressive strain and Mn doping on tuning the structure and magnetic behavior of BiFeO₃ thin films

BiFe_1-xMn_xO₃ (BFMO) films (x = 0, 0.05, 0.1) were grown on (001) LaAlO₃ (Lao) substrates to demonstrate the role of chemical pressure on the lattice structure and magnetic behaviors of compressively-strained BiFeO₃ (BFO) films. The structural analyses indicated that the substitution of Jahn-Teller active ion Mn at Fe site tuned the ferroelectric distortion and antiferrodistortive (AFD) rotation in BFO lattice, thus weakened the tetragonal-like (T-like) phase originated from the large substrate clamping. The phase transition mechanism was discussed to reveal the competition between inner lattice distortion and external stress in BFO films. Clear domain variants change from (T-like) phase to rhombohedral-like (R-like) phase provided further evidence for the structure alteration. Meanwhile the gradual relaxation in total lattice strain of BFMO films with increasing x reduced the magnetism contribution from the strong spin and lattice coupling.