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First-order structural transition in the multiferroic perovskite-like formate [(CH3)2NH2][Mn(HCOO)3]

2014; Royal Society of Chemistry; Volume: 16; Issue: 17 Linguagem: Inglês

10.1039/c3ce42411a

1466-8033

Manuel Sánchez‐Andújar, L. C. Gómez-Aguirre, Breogán Pato‐Doldán, S. Yáñez‐Vilar, Ramón Artiaga, A.L. Llamas-Saiz, R.S. Manna, F. Schnelle, Michael Lang, Franz Ritter, Amir A. Haghighirad, M. A. Señarís‐Rodríguez,

Perovskite Materials and Applications

In this work we explore the overall structural behaviour of the [(CH3)2NH2][Mn(HCOO)3] multiferroic compound across the temperature range where its ferroelectric transition takes place by means of calorimetry, thermal expansion measurements and variable temperature powder and single crystal X-ray diffraction. The results clearly prove the presence of a structural phase transition at Tt ~ 187 K (the temperature at which the dielectric transition occurs) that involves a symmetry change from Rc to Cc, twinning of the crystals, a discontinuous variation of the unit cell parameters and unit cell volume, and a sharp first-order-like anomaly in the thermal expansion. In addition, the calorimetric results show a 3-fold order–disorder transition. The calculated pressure dependence of the transition temperature is rather large (dTt/dP = 4.6 ± 0.1 K kbar−1) in that it should be feasible to shift it to room temperature under adequate thermodynamic conditions, for instance by application of an external pressure.