An intriguing magnetodielectric (MD) behavior is observed in geometrically frustrated spin-tetrahedral systems Cu2Te2O5X2 (X = Cl and Br). While the phase transition observed in the Cl-system at TN=18.5 K is consistent with 3D antiferromagnetic ordering, the phase transition at To=11.5 K in the Br-system has several unusual features. Concomitantly, a pronounced ferroelectric ordering is observed coinciding with TN of Cl-system and To of Br-system. At the highest applied magnetic field 90 kOe, the temperature dependent dielectric behavior with almost frequency independent well defined at TN~18.5 K are decrease compared with that at zero field for Cl-system, and at the highest applied magnetic field 90 kOe, the temperature dependent dielectric behavior with almost frequency independent well defined at Tm~30 K are decrease compared with that at zero field for Br-system. The ferroelectricity is ascribed to the polarization of the Te4+ lone-pair electrons, while the MD effect is argued to be due to exchange interaction involving frustrated tetramer clusters and intercluster exchange bridges.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0628112-172705 |
| Date | 28 June 2012 |
| Creators | Yeh, Chin-Chia |
| Contributors | Hsiung Chou, Jiunn-Yuan Lin, Hung-Duen Yang, Jim-Long Her |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0628112-172705 |
| Rights | user_define, Copyright information available at source archive |
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