A-Site Ordering versus Electronic Inhomogeneity in Colossally Magnetoresistive Manganite Films

V. Moshnyaga, L. Sudheendra, O. I. Lebedev, S. A. Köster, K. Gehrke, O. Shapoval, A. Belenchuk, B. Damaschke, G. van Tendeloo, K. Samwer
2006 Physical Review Letters  
Epitaxial La3/4Ca1/4MnO3/MgO(100) (LCMO) thin films show unusual rhombohedral (R-3c) structure with a new perovskite superstructure due to unique ordering of La and Ca at the A-site positions. Very sharp insulator-metal and para-ferromagnetic phase transitions at temperatures up to TMI ~ TC=295 K were observed. The ordered films were electronically homogeneous down to 1 nm scale as revealed by scanning tunnelling microscopy/spectroscopy. In contrast, orthorhombic and A-site disordered LCMO
more » ... strate broadened phase transitions as well as mesoscopic phase separation for T<<TC. The unique La/Ca ordering suppresses cation mismatch stress within one super-cell, a~1.55 nm, enhancing electronic homogeneity. Phase separation scenario seems not to be a unique mechanism for CMR as very large CMR=500 % was also observed in A-site ordered films.
doi:10.1103/physrevlett.97.107205 pmid:17025850 fatcat:hhvyitokvbad3ibzbszunq75f4