The nanomechanical properties of BiFeO3 (BFO) thin films are subjected to nanoindentation evaluation. BFO thin films are grown on the Pt/Ti/SiO2/Si substrates by using radio frequency magnetron sputtering with various deposition temperatures. The structure was analyzed by X-ray diffraction, and the results confirmed the presence of BFO phases. Atomic force microscopy revealed that the average film surface roughness increased with increasing of the deposition temperature. A Berkovich nanoindenter operated with the continuous contact stiffness measurement option indicated that the hardness decreases from 10.6 to 6.8 GPa for films deposited at 350°C and 450°C, respectively. In contrast, Young's modulus for the former is 170.8 GPa as compared to a value of 131.4 GPa for the latter. The relationship between the hardness and film grain size appears to follow closely with the Hall–Petch equation.

Highly textured BiFeO3(001) films were formed on L10-FePt(001) bottom electrodes on glass substrates by sputtering at reduced temperature of 400°C. Good electric polarization 2Pr = 80 and 95 μC/cm2, comparable to that of the reported epitaxial films, and coercivity Ec = 415 and 435 kV/cm are achieved in the samples with 20-nm- and 30-nm-thick electrodes. The BiFeO3(001) films show different degrees of compressive strain. The relation between the variations of strain and 2Pr suggests that the enhancement of 2Pr resulted from the strain-induced rotation of spontaneous polarization. The presented results open possibilities for the applications based on electric-magnetic interactions.