Nanostruktūrizuotų manganitų kobaltitų sluoksnių magnetovaržinės savybės /

In this doctoral dissertation the magnetoresistance properties of manganite films La1 xSrxMnzO3 doped with cobalt (La1−xSrx(Mn1−yCoy)zO3) were investigated. The resistivity vs. temperature dependences and metal semiconductor transition temperature dependence on the degree of cobalt doping and the size of crystallites in the films were investigated. The resistance relaxation processes in these films after switching-off the magnetic field and the origin of phenomena determining these processes were studied. The influence of long term and accelerated aging of the films on their magnetoresistive properties were investigated. It has been found that cobalt doping of manganite films increases the resistivity values of manganite cobaltite films and shifts the metal semiconductor transition temperature to the lower temperature range, as well as increases the magnetoresistance values. It was found that the ‘fast’ component of the relaxation process is determined by the formation of nucleation centers of the magnetic domains and their reorientation to equilibrium state, while the ‘slow’ component is due to the processes taking place in the disordered grain boundary areas of the films. The dynamics of these processes are well described by Kolmogorov Avrami Fatuzzo model with a compressed exponent and Kohlrausch Williams Watts model with an stretched exponent, respectively. The aging processes of the films results in an increase in resistance due to the depletion and diffusion of oxygen through the grain boundary areas to the surface of the films. Based on the obtained results, a prototype of a magnetic field sensor for measurements at cryogenic temperatures was developed.

Grantor dc:publisher

Institutional Repository of Vilnius University

Year dc:date

2021

Author dc:creator

• Rudokas, Vakaris,

Contributors dc:contributor

• Žurauskienė, Nerija

• colossal magnetoresistance (CMR) ; nanostructured manganite thin films ; magnetic field sensors

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

lit

Repository record dc:identifier

https://repository.vu.lt/VU:ELABAETD114586735&prefLang=en_US

OAI identifier oai:identifier

oai:vu.lt:elaba:114586735