High-temperature elastic measurements in La273Sr1/3MnO3 at low frequency

SEIRO, SILVIA; GHILARDUCCI, ADA; SALVA, HORACIO; VASQUEZ MANSILLA, MARCELO; SAINT-PAUL, M.; LEJAY, P.; MONCEAU, P.

Recife, Brasil

Conferencia; International Conference on Magnetism; 2000

In the present work, we report elastic measurements performed on the manganese perovskite La2/3Sr1/3MnO3, for which the ferromagnetic ordering temperature was determined to be 377 K, coincident with a metal–insulator transition. Measurements in the temperature range 250–480 K at various frequencies were performed, showing a weak dip in the modulus (1.9%) and no Q−1 peak at the magnetic transition, unlike La2/3Ca1/3MnO3. Two Q−1 peaks were observed, one above Tc (414.5±0.2 K at 1 Hz) and another below Tc (303±6 K at 1 Hz). With increasing measurement frequency between 0.3 and 20 Hz, a shift to higher temperatures of the centers of both peaks was observed. Such shifts yielded an activation energy of 3.77±0.05 eV for the high-temperature peak and 0.56±0.07 eV for the low-temperature peak. Evidence was found that the high-temperature peak is not a simple relaxation process, but shows a relaxation time distribution. Relaxation peaks are attributed to jumps of oxygen ions within the crystal under applied stress.