The complex magnetic behavior and the role of dynamic structural fluctuations in La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} crystals.
- Univ. of Maryland (US)
The layered perovskite double sheet La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} crystals have shown an unusual magnetic behavior. They are found to be fully ferromagnetic below 120 K, with a small ferromagnetic component ({le} 0.3% by volume) persisting above 120 K and extending up to 320 K along with a paramagnetic phase and becoming fully paramagnetic above 320 K. A large magnetoresistance is seen around 120 K. Ion channeling investigations in these crystals show clearly a change of 1.5 picometer in the atomic displacement from 70 to 150 K, which is twice than that expected due to the change in the thermal vibrational amplitude and the lattice parameters a and c, observed by neutron diffraction. This provides a clear indication of dynamic distortion occurring around the ferromagnetic transition. Even in the wide temperature region between 120 to 320 K, anomalous displacement of ions can be seen, correlating well with the features observed in magnetization measurements. These displacements are again larger than those due to thermal motion, thereby supporting the idea of dynamic fluctuations in the Jahn-Teller distorted MnO{sub 6} octahedra playing an important role at the magnetic phase transitions in this material. There is a large magneto-crystalline anisotropy with the hard axis along the c-direction. The material seems to be an inhomogeneous magnetic system with the presence of small regions of highly correlated spins parallel to the ab plane and appears to be in a state of two dimensional magnetic order in the region 120 to 320 K.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 10557
- Report Number(s):
- ANL/MSD/CP-95294; TRN: AH200126%%307
- Resource Relation:
- Conference: 43rd Annual Conference on Magnetism and Magnetic Materials, San Francisco, CA (US), 01/06/1998--01/09/1998; Other Information: PBD: 12 Jan 1998
- Country of Publication:
- United States
- Language:
- English
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