Lanthanum strontium manganite

Lanthanum strontium manganite (LSM or LSMO) is an oxide ceramic material with the general formula La1-xSrxMnO3, where x describes the doping level and for some applications it is in the range of 10-20%.[1]

It has a perovskite-based crystal structure, which has the general form ABO3. In the crystal, the 'A' sites are occupied by lanthanum and strontium atoms, and the 'B' sites are occupied by the smaller manganese atoms. In other words, the material consists of lanthanum manganite with some of the lanthanum atoms substitutionally doped with strontium atoms. The strontium (valence 2+) doping on lanthanum (valence 3+) introduces extra holes in the valence band and thus increases electronic conductivity.

LSMO has a rich electronic phase diagram, including a doping-dependent metal-insulator transition, paramagnetism and ferromagnetism.[2] Evidence of the existence of a Griffith phase has been reported as well.[3][4]

LSM is black in color and has a density of approximately 6.5 g/cm3.[5] The actual density will vary depending on the processing method and actual stoichiometry. LSM is primarily an electronic conductor, with transference number close to 1.

This material is commonly used in as a cathode material in commercially produced solid oxide fuel cells (SOFCs) because it has a high electrical conductivity at higher temperatures, and its thermal expansion coefficient is well matched with yttria-stabilized zirconia (YSZ), a common material for SOFC electrolytes.

In research, LSM is one of the perovskite manganites that show the colossal magnetoresistance (CMR) effect,[6] and is also an observed half-metal for compositions around x=0.3.[7]

LSM behaves like a half-metal, suggesting its possible use in spintronics. It displays a colossal magnetoresistance effect. Above its Curie temperature (about 350K) Jahn-Teller polarons are formed; the material's ability to conduct electricity is dependent on the presence of the polarons.[8]

See also

References

  1. ↑ "Lanthanum Strontium Manganite Supplier & Tech Info". American Elements. Retrieved 2008-04-19.
  2. ↑ A. Urushibara; et al. (1995). Physical Review B. 51: 14103. doi:10.1103/PhysRevB.51.14103. Missing or empty |title= (help)
  3. ↑ J. Deisenhofer; et al. (2005). Physical Review Letters. 95: 257202. Bibcode:2005PhRvL..95y7202D. doi:10.1103/PhysRevLett.95.257202. Missing or empty |title= (help)
  4. ↑ E. Dagotto (2003). "Nanoscale Phase Separation and Colossal Magnetoresistance. The Physics of Manganites and Related Compounds". Springer.
  5. ↑ Performance of Solid Oxide Fuel Cells with LSGM-LSM Composite Cathodes, J. Electrochem. Soc., Volume 149, Issue 12, pp. A1565-A1571 (2002)
  6. ↑ A P Ramirez (1997) Colossal magnetoresistance. J. Phys.: Condens. Matter 9, 8171-8199.
  7. ↑ J H Park et al (1998) Direct evidence for a half-metallic ferromagnet. Nature 392, 794-796.
  8. ↑ "Berkeley Lab View -- April 29, 2005". lbl.gov. Retrieved 17 May 2015.


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