Lattice effects and magnetic structure in the layered colossal magnetoresistance manganite La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7}, x = 0.3.
We report on the temperature dependence of the crystal and magnetic structure of the layered colossal magnetoresistive manganite, La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7}, x=0.3. Neutron-diffraction measurements show that the insulator-metal (IM) transition (T{sub IM}) at -100 K is accompanied by a ferromagnetic (FM) ordering of spins within MnO{sub 6} bilayers (intrabilayer coupling), but with an antiferromagnetic coupling between neighboring bilayers (interbilayer coupling). Below T{sub IM}, the Mn spins rotate from -45{sup o} inclination to the c axis until they are almost parallel to the c axis at 5 K. Coincident with this spin reorientation, a FM c axis component develops below 75 K. Evidence from both neutron and synchrotron x-ray-diffraction experiments suggest that the FM c-axis magnetic moment results from a second layered manganite phase with composition 0.3{<=}x{<=}0.32. This observation emphasizes the need for thorough examination of the homogeneity when measuring bulk properties (e.g., magnetization, transport) of nominally x=0.3 samples. Associated with the electronic and magnetic transitions, a pronounced lattice response along the c axis (observed in both phases) signals a transfer of charge into d{sub x{sup 2}-y{sup 2}} orbitals in the low-temperature phase. That the lattice effects here are opposite in sign to those observed in the x=0.4 layered manganite points to the sensitivity of the spin-lattice-charge coupling to dopant concentration in these reduced-dimensionality manganites.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- ER
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 942396
- Report Number(s):
- ANL/MSD/JA-30983; TRN: US0902824
- Journal Information:
- Phys. Rev. B, Vol. 59, Issue 13 ; Apr. 1999; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
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