Relaxation Phenomenon in the Formation of the C-Type Orbital-Ordered State in the Simple Perovskite Manganite Sr^sub 1-x^Nd^sub x^MnO^sub 3

• Published in: Journal of the Physical Society of Japan 2016-02, Vol.85 (2), p.1
• Main Authors: Inoue, Yasuhide, Sato, Hiroki, Koyama, Yasumasa
• Format: Article
• Language: English
• Subjects: Perovskite; Symmetry; Transmission electron microscopy
• ISSN: 0031-9015; 1347-4073

The formation of the C-type orbital-ordered (COO) state from the disordered cubic (DC) state in ... (SNMO) with the simple perovskite structure has been examined mainly by transmission electron microscopy. As the COO state has tetragonal I4/mcm symmetry, its formation is associated with the cubic-to-tetragonal structural transition. It was found that, when SNMO samples were cooled down from the DC state, the R25-type rotational displacement of MnO6 octahedra was first induced, together with the symmetry change into the tetragonal I4/mcm structure. The C-type orbital ordering then appeared due to the induction of the Jahn-Teller distortion as a response of a lattice system to this orbital ordering. Because no symmetry change occurred in the latter case, the Jahn-Teller distortion can be regarded as a dilatational distortion. One interesting feature is that the appearance of the dilatational Jahn-Teller distortion led to a nanometer-scale banded structure, characterized by an alternating array of two tetragonal variants with different c/a values. In addition, the formation of the COO state from the DC state exhibited a time-relaxation phenomenon. The origin of this relaxation phenomenon is also discussed here in terms of the competition between the tetragonal spontaneous strain for the rotational displacement and the dilatational Jahn-Teller distortion for orbital ordering. (ProQuest: ... denotes formulae/symbols omitted.)