Investigation on the low-frequency mechanical properties of La0.6Sr0.4Co1−xFexO3−δ materials

The low-frequency mechanical properties of La0.6Sr0.4Co1−xFexO3−δ (0 ≤ x ≤ 0.8) materials have been measured using a computer-controlled pendulum. For undoped sample, five internal friction peaks (P0, P1, P2, P3 and P4) were observed. However, with the Fe doping, only two peaks (P3 and P4) were found at high temperature. The peaks of P0 and P1 have the feature of phase transition-induced internal friction, while the peaks of P2, P3 and P4 are the relaxation-type. From the analysis, it is suggested that the peak of P0 is due to the phase separation and the peak of P1 is related to the ferromagnetic (FM)–paramagnetic (PM) phase transition. For the peaks of P2, P3 and P4, they were associated with the motion of domain walls. The formation of this kind of domain structure is a consequence of a transformation from the paraelastic cubic phase to ferroelastic rhombohedral phase.

Research highlights
► In this paper, in order to clarify the nature of some phase transitions and origin of inelastic information, we carried out an investigation on the mechanical properties of La0.6Sr0.4Co1−xFexO3−δ (0 ≤ x ≤ 0.8) materials by using low frequency internal friction technique. The results show that the inelastic deformation of La0.6Sr0.4Co1−xFexO3−δ materials can be understood in virtue of the motion of domain walls, and domains were formed during the cubic–rhombohedral phase transition. Below the ferromagnetic ordering temperature TC, La0.6Sr0.4CoO3−δ system presents a phase transition, which is related to magnetization intrinsic phase separation.