Anomalous variation of the mechanical behaviour of ferroelastic La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ during the ferro-to-paramagnetic transition

Uniaxial compression tests of ferroelastic La0.6Sr0.4Co0.2Fe0.8O3-δ were conducted in the temperature range covering the ferro-to-paramagnetic transition at ∼240 K (Tc). An anomalous variation of mechanical behaviour was observed. The apparent elastic modulus drastically decreases above Tc, whilst it is almost constant below Tc; on the other hand, the critical stress for ferroelastic domain switching decreases monotonically with increasing temperature. Furthermore, the back-switching occurs easily and/or rapidly below Tc, but the material becomes brittle.