Intrinsic properties of doped lanthanum manganite

Book · Fri Nov 01 04:00:00 EST 1996

OSTI ID:392208

Snyder, G J; Beasley, M R; Geballe, T H ^[1]; Hiskes, R; DiCarolis, S ^[2]

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1. Stanford Univ., CA (United States). Dept. of Applied Physics
2. Hewlett-Packard, Palo Alto, CA (United States)

An investigation designed to display the intrinsic properties of perovskite manganites was accomplished by comparing the behavior of bulk samples with that of thin films; the results show the colossal magneto resistance at very low temperatures is not an intrinsic property of the thermodynamically stable 1/3 doped material. Epitaxial 1,500 {angstrom} films of perovskite La{sub 0.67}Ca{sub 0.33}MnO{sub 3} and La{sub 0.67}Sr{sub 0.33}MnO{sub 3} were grown by solid source chemical vapor deposition on LaAlO{sub 3} and post annealed in oxygen at 950 C. Below Tc/2 the intrinsic magnetization decreases as T{sup 2} (as can be expected for itinerant electron ferromagnets) while the intrinsic resistivity increases proportional to T{sup 2}. The constant and T{sup 2} coefficients of the resistivity are largely independent of magnetic field and alkaline earth element (Ca, Sr or Ba). The authors identify three distinct types of negative magnetoresistance. The largest effect is observed near the Curie temperature and is likely to be due to magnetic critical scattering. There is also magnetoresistance associated with the net magnetization of polycrystalline samples. The high temperature (above {Tc}) resistivity at La{sub 0.67}Ca{sub 0.33}MnO{sub 3} is consistent with small polaron hopping conductivity with a transition at 750K, while La{sub 0.67}Sr{sub 0.33}MnO{sub 3} does not exhibit activated conductivity until about 500K, well above {Tc}. The limiting low and high temperature resistivities may place a limit on the maximum possible magnetoresistance of these materials.

• OSTI ID: 392208
• Report Number(s): CONF-951155--; ISBN 1-55899-304-5
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINATES
ANNEALING
CALCIUM OXIDES
CHEMICAL VAPOR DEPOSITION
CUBIC LATTICES
CURIE POINT
EXPERIMENTAL DATA
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LASERS
MAGNETIC FIELDS
MAGNETIC PROPERTIES
MAGNETIZATION
MAGNETORESISTANCE
MANGANESE OXIDES
OXYGEN
PEROVSKITES
STRONTIUM OXIDES
SUBSTRATES
TEMPERATURE DEPENDENCE
X-RAY DIFFRACTION