Study of colossal magnetoresistance and pressure effects in La2/3Ca1/3MnO2 thin films /

The main purpose of this thesis is to study properties of La2/3Cai/3Mn03, both polycrystalline ceramics and thin films. This material has striking related electrical and magnetic properties. Thin films show colossal negative magnetoresistance (CMR) near transition from an insulating to a metallic state accompanied closely by transition from a paramagnetic to a ferromagnetic state. The double exchange mechanism (DE) and the Jahn-Teller deformations play an important role in CMR effect. Applied pressure has a very similar effect as does an applied magnetic field, except, at low temperatures (T<Tc) the field suppresses the resistivity more than pressure. In our study we performed x-ray diffraction analysis, resistivity and magnetization measurements, as well as measurements of resistivity under applied pressure. The origin of strong resistivity change at low temperatures can be explcdned by the intergranular spin-dependent scattering of DE electrons. Oxygen stoichiometry plays an important role in the magnitude and position of MR(T) maximum. The distortions of structure and Mn-O-Mn bonds in applied pressure axe discussed. The fabrication of La2/3Cai/3Mn03 thin films by pulsed laser deposition was successfully developed. The films grown on (100) SrTiOs substrate are c-axis oriented and exhibit negative magnetoresistance Ap/p(H) of over 400% at 245°C and 4200% at 90 K.

Name thesis:degree_name

M.Sc. Physics

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Faculty of Mathematics and Science

Department dc:contributor.department

Department of Physics

Grantor

Brock University

Year dc:date.issued

1998

Author dc:creator

• Roch, Tomás.

• Lanthanum compounds.
• Manganese.
• Magnetoresistance.
• Thin films

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/10464/1344

OAI identifier oai:identifier

oai:brocku.scholaris.ca:10464/1344