Structural, transport and magnetic studies of perovskite Bi1-x Cax Mn O3

Author

Hyungje Woo, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

Summer 8-31-2001

Degree Name

Doctor of Philosophy in Applied Physics - (Ph.D.)

Department

Federated Physics Department

First Advisor

Trevor Tyson

Second Advisor

Mark C. Croft

Third Advisor

S.-W. Cheong

Fourth Advisor

Earl David Shaw

Fifth Advisor

Gordon A. Thomas

Abstract

This dissertation presents an investigation of the fundamental physics of the perovskite system Bi_1-xCa_xMn0₃. This material belongs to a group of simple perovskites called the manganites which are of technological importance for magnetic device applications as read-head sensors.

The Bi_1-xCa_xMnO₃ system is known to exhibit charge ordering (and high sensitivity to magnetic fields) for a much broader range of x than the well-characterized La_1-xCa_xMnO₃ system. However, the properties of Bi_1-xCa_xMnO₃ over the entire doping range are not well understood. Magnetization and resistivity measurements (up to 30T) as well as x-ray absorption and x-ray diffraction measurements on Bi_1-xCa_xMnO₃ were performed to correlate the structural, transport, and magnetic properties. The system was found to be insulating and antiferromagnetic for the entire range of x studied (x ≥ 0.4) except near x ~ 0.875 where glassy behavior was observed. Detailed magnetization measurements were performed as a function of field and temperature to explore the net moment on the Mn sites as a function of x. These measurements reveal the charge ordering and N6el temperatures. X-ray absorption measurements reveal significant structural distortions of the Mn-0 bond distributions with increasing Bi content that correlates directly with increasing charge-ordering temperatures. Moreover, x-ray diffraction data reveal peak splittings consistent with lower symmetry cells as the Bi content increases. These structural-magnetic correlations point to the importance of Mn0 distortions in stabilizing the charge-ordered state in the manganites. A structural, transport and magnetic phase diagram over the complete range of x has been developed.

Recommended Citation

Woo, Hyungje, "Structural, transport and magnetic studies of perovskite Bi1-x Cax Mn O3" (2001). Dissertations. 507.
https://digitalcommons.njit.edu/dissertations/507