|Author's Email Address
||This thesis had been viewed 5586 times. Download 454 times.|
||International PhD Program for Synchrotron Radiation and Neutron Beam Applications|
|Type of Document
||Novel properties in spin-frustrated systems Cu2OSeO3, Cu2OCl2, and Cu3Bi(SeO3)2O2Cl|
|Date of Defense
||The purpose of this dissertation is to study three geometrical spin-frustrated systems, such as the corner-sharing of tetrahedron in Cu2OSeO3, pyrochlore structure in Cu2OCl2, and Kagome lattice in Cu3Bi(SeO3)2O2Cl.|
Novel skyrmion phase in Cu2OSeO3 is a remarkable characteristic as a vortex-like spin configuration in specific magnetic field and temperature region. Using the effects of compression pressure, chemical expansion, non-magnetic (Zn) and magnetic (Ni) element doping on Cu2OSeO3, outstanding and interesting research findings were investigated. The skyrmion phase region becomes split upon Zn doping concentration. Large enhancement of skyrmion area upon Ni-doped could be ascribed to the magnetic anisotropy of the Jahn-Teller active Ni2+ ion in Cu(I) site. Under the external pressure, the skyrmion zone is enlarged owing to the enhancement of strengths of competing Dzyaloshinsky–Moriya (DM) and Heisenberg exchange (J) interactions. Skyrmion zone is gradually suppressed with Te doping, which could be related to the decrease of D/J parameter.
Temperature and magnetic field dependent magnetization, specific heat, dielectric, and polarization properties in pyrochlore Cu2OCl2 and Kagome single crystal Cu3Bi(SeO3)2O2Cl were established as new type-II multiferroics. The mechanism of multiferroic behavior in Cu2OCl2 is related to the inverse Dzyaloshinskii–Moriya (DM) interaction. Furthermore, the key mechanism of the anisotropic spin-flip induced multiferroicity in Cu3Bi(SeO3)2O2Cl can be ascribed to the breaking of magnetic two-fold symmetry in the bc plance above Hc.
||Chien-Cheng Kuo - chair|
Jim-Long Her - co-chair
Wen-Hsien Li - co-chair
Jiunn-Yuan Lin - co-chair
Hung-Duen Yang - advisor
Indicate in-campus at 1 year and off-campus access at 1 year.|
|Date of Submission