Jahn-Teller distortion ordering in single-crystal Nd1/2Sr1/2MnO3

• Published in: Physica status solidi. C Vol. 1; no. 7; pp. 1641 - 1644
• Main Authors: Ghazi, Mohammad E., Hatton, P. D.
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.05.2004; WILEY‐VCH Verlag
• Subjects: 60.10.−i; 64.60.−i; 71.30.+h
• ISSN: 1610-1634; 1610-1642
• DOI: 10.1002/pssc.200304405

Charge, spin and orbital degrees of freedom play important roles in the electrical and magnetic properties of manganites. Nd0.5Sr0.5MnO3 is a paramagnetic insulator with Imma orthorhombic symmetry at room temperature. Upon cooling it becomes a ferromagnetic metal below 240 K and at 160 K undergoes a first‐order phase transition. Below this temperature it is a CE‐type antiferromagnetic insulator. In this paper we report synchrotron X‐ray scattering investigations of superlattice reflections observed in the low temperature phase of Nd0.5Sr0.5MnO3. Upon cooling below 160 K we observed additional peaks occurring at non‐integer positions in reciprocal space. These reflections had a wavevector (1/2, 0, 0) and are due to the structural modulation arising from the Jahn‐Teller distortion associated with charge ordering of Mn3+ and Mn4+ ions and orbital ordering in the sample. The peaks observed below 160 K have an intensity of approximately 10−3 that of the Bragg reflections. The intensity profiles of these reflections show that the transition into the ordered phase is strongly first‐order. The structural phase transition was observed to display a hysteresis width of 10 K. The measured widths of these peaks show that the charge modulation is correlated primarily in the ac plane rather than the K‐direction (long‐axis). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)