Interplay between charge, spin and orbital ordering in La 1 - Kappa Sr Kappa MnO 3 manganites

Strongly correlated electron systems are of great interest due to their possible applications in technology. These materials are characterized by a wide variety of ground states. In many cases transitions between these ground states can be driven by relatively small changes in the chemical doping or temperature. The origin of such unusual sensitivity is believed to be in interplay between competing degrees of freedom. In this work interplay between charge, orbital and spin ordering in lightly doped La1-xSrxMnO3 with x~1/8 has been studied using both resonant and non-resonant (high-energy) X-ray scattering (at Advance Photon Source at Argonne National Laboratory and HASY Lab at DESY) as well as neutron scattering (Research Reactor at Forschungszentrum Jülich). The work consists of introduction including the basic theory of the manganites and their properties; review and critics of experimental works devoted to the interpaly between charge, spin and orbital ordering; explanation of sample preparation; experimental procedures and results. A new technique for preparation of single-phase manganite powders has been developed and approved for a series of powder samples with different stoichiometry. A series of good quality single crystals has been obtained using the floating-zone single crystal growing method at the Institute of Crystallography (RWTH Aachen). The single crystals have been extensively studied by macroscopic and scattering methods. Results from the experiments firmly show that the resonant X-Ray scattering method can not be treated as direct probe of orbital ordering phenomena which is in contrary to early claims by other groups. Resonant intensities on the forbidden (1,0,0) and (3,0,0) reflections are correlated to the cooperative JT-distortions. No sharp transition to "orbital ordered phase" is observed. Non-resonant X-Ray experimental data reveals a second order transition to a charge ordered phase below 120 K. Results of the neutrons scattering experiments show a large amount of diffuse scattering around main Bragg peaks. Using polarization analysis it is shown that the diffuse scattering can be effectively separated to nuclear coherent and paramagnetic scattering, the latter is dominating above the Curie temperature. The diffuse scattering can be well fitted with the main field theory, giving experimentally the value of the exchange integral.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2003

Author dc:creator

• Istomin, Konstantin

Contributors dc:contributor

• Brückel, Thomas

• info:eu-repo/classification/ddc/530
• Physik
• Manganate
• Ladungsordnung
• Spinordnung
• Orbitalordnung

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-120610%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:58775