Spontaneous magnetostriction in La2/3(Ca1−x Srx) 1/3MnO3 (x=0, 0.05, 0.15, 0.25 and 1.0) near TC and its field dependence

We report thermal expansion measurements in La2/3(Ca 1-xSrx) 1/3MnO3perovskites. For x = 0 and 0.05 a very narrow and symmetric cusp is observed, at Tc, indicating the transition is first order, changing to second order above x = 0.15. The data of an x = 1 single crystal was fitted in the critical region yielding α = - 0.14 ± 0.10 for the critical exponent and A +/A- = 1.4 ± 0.4 for the amplitude ratio, both characteristic of 3d-Heisenberg systems. The magnetic field dependence is observed to decrease with increasing x. © 2001 Elsevier Science B.V. All rights reserved.