Successive phase transitions in a metal-ordered manganite perovskite YBaMn2O6

Structural, magnetic and electric properties of a metal-ordered perovskite YBaMn2O6 have been studied by means of powder X-ray diffraction, differential scanning calorimetric, magnetic susceptibility, and electric resistivity. It is found that this material undergoes a first-order structural phase transition at T-cl = 520 K, from a pseudo orthorhombic (monoclinic) phase (T-cl < T) to a pseudo tetragonal (monoclinic) one (T < T-cl). Accompanied by this transition the susceptibility exhibits a sharp drop where ferromagnetic exchange interaction becomes antiferromagnetic. Furthermore, two more transitions, a metal-insulator transition at T-c2 = 480 K and an antiferromagnetic ordering at T-c3 = 200 K, have been observed, respectively. (C) 2002 Elsevier Science Ltd. All rights reserved.