Giant magnetostructural coupling in Gd_2/3Ca_1/3MnO₃

We report high magnetic field magnetostructural studies on Gd_2/3Ca_1/3MnO₃ single crystals. A giant linear magnetostrictive effect is observed in a wide temperature range (T < 120 K). Above 25 K a large hysteresis is seen reflecting the Mn magnetic moments ordering. At lower temperature (T < 15 K), a rather complicated field dependence arising from the competition between the Mn and Gd magnetic sublattices is observed. The relevance of the Gd ions in the low temperature behavior is further corroborated by specific heat experiments.