國立高雄大學圖資館 |

Language: English

Back

Magnetic properties of copper pyrazi...

Clark University.

Magnetic properties of copper pyrazine bridged quasi two dimensional quantum Heisenberg antiferromagnetic (QHAF) compounds.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Magnetic properties of copper pyrazine bridged quasi two dimensional quantum Heisenberg antiferromagnetic (QHAF) compounds.
Author:	Xiao, Fan.
Description:	88 p.
Notes:	Source: Dissertation Abstracts International, Volume: 72-07, Section: B, page: .
Notes:	Adviser: Christopher Landee.
Contained By:	Dissertation Abstracts International72-07B.
Subject:	Physics, Quantum.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3455151
ISBN:	9781124623689

Magnetic properties of copper pyrazine bridged quasi two dimensional quantum Heisenberg antiferromagnetic (QHAF) compounds.
Xiao, Fan.

Magnetic properties of copper pyrazine bridged quasi two dimensional quantum Heisenberg antiferromagnetic (QHAF) compounds. - 88 p.

Source: Dissertation Abstracts International, Volume: 72-07, Section: B, page: .

Thesis (Ph.D.)--Clark University, 2011.

The magnetic properties of a family of molecular-based quasi-two-dimensional S=1/2 Heisenberg antiferromagnets (2D QHAF) are studied. Three compounds, Cu(pz)2 (ClO4)2, Cu(pz)2(BF 4)2, and [Cu(pz)2(NO3)](PF6) contain similar planes of Cu2+ ions linked into magnetically square lattices by bridging pyrazine molecules (pz =C4H4N 2). The anions provide charge balance as well as isolation between the layers. Low field single crystal measurements of susceptibility and magnetization reveal low ratios of Neel temperatures to exchange strengths (4.25/17.5 = 0.243, 3.80/15.3 = 0.248, and 3.05/10.8 = 0.282, respectively) while the ratio of the anisotropy fields HA(kOe) to the saturation field HSAT(kOe) are small (2.6/490 = 5.3x10-3, 2.4/430 = 5.5x10-3, and 0.07/300 = 2.3x10-4, respectively), demonstrating close approximations to a two-dimensional Heisenberg model.

ISBN: 9781124623689Subjects--Topical Terms:

530960
Physics, Quantum.

Magnetic properties of copper pyrazine bridged quasi two dimensional quantum Heisenberg antiferromagnetic (QHAF) compounds.
LDR:03349nmm 2200325 4500 001 309717
005 20111105132454.5
008 111212s2011 ||||||||||||||||| ||eng d
020 $a 9781124623689
035 $a (UMI)AAI3455151
035 $a AAI3455151
040 $a UMI $c UMI
100 1 $a Xiao, Fan. $3 531054
245 1 0 $a Magnetic properties of copper pyrazine bridged quasi two dimensional quantum Heisenberg antiferromagnetic (QHAF) compounds.
300 $a 88 p.
500 $a Source: Dissertation Abstracts International, Volume: 72-07, Section: B, page: .
500 $a Adviser: Christopher Landee.
502 $a Thesis (Ph.D.)--Clark University, 2011.
520 $a The magnetic properties of a family of molecular-based quasi-two-dimensional S=1/2 Heisenberg antiferromagnets (2D QHAF) are studied. Three compounds, Cu(pz)2 (ClO4)2, Cu(pz)2(BF 4)2, and [Cu(pz)2(NO3)](PF6) contain similar planes of Cu2+ ions linked into magnetically square lattices by bridging pyrazine molecules (pz =C4H4N 2). The anions provide charge balance as well as isolation between the layers. Low field single crystal measurements of susceptibility and magnetization reveal low ratios of Neel temperatures to exchange strengths (4.25/17.5 = 0.243, 3.80/15.3 = 0.248, and 3.05/10.8 = 0.282, respectively) while the ratio of the anisotropy fields HA(kOe) to the saturation field HSAT(kOe) are small (2.6/490 = 5.3x10-3, 2.4/430 = 5.5x10-3, and 0.07/300 = 2.3x10-4, respectively), demonstrating close approximations to a two-dimensional Heisenberg model.
520 $a The susceptibilities of Cu(pz)2(ClO4)2 and Cu(pz)2(BF4)2 show evidence of a spin crossover (Heisenberg to XY) at low temperatures; their zero-field ordering transitions are primarily driven by the XY behavior with the ultimate three-dimensional transition appearing parasitically. The [Cu(pz)2(NO 3)](PF6) compound remains Heisenberg-like at all temperatures, with its transition to the Neel state due to the inter- layer interactions.
520 $a High field single crystal measurements of Cu(pz)2(ClO 4)2 indicates that both spin crossover transition temperature and ordering temperature increase as the external field increases up to 5 T. The results suggests a field-induced XY anisotropy is produced by the external field and the ordering temperature vs field follows a Berezinskii-Kosterlitz-Thouless (BKT)-like transition trend predicted by quantum Monte Carlo simulation.
520 $a Calorimetry measurements were performed to verify the hypothesis with external fields up to 33 T. The results successfully confirmed our prediction. The transition temperature shows a rounded maximum at 16 T and starts dropping as the field gets stronger. The ordering temperature is raised by as much as 41% (6 K) at 16 T and drops down to around 4.5 K at 33 T.
520 $a These three compounds serve as very good examples of 2D QHAF for testing the theoretical predictions, and they have shown the unique magnetic behavior that only exists at extreme conditions, such as a spin Heisenberg to XY crossover and BKT-like transition.
590 $a School code: 0048.
650 4 $a Physics, Quantum. $3 530960
650 4 $a Physics, Electricity and Magnetism. $3 227483
690 $a 0599
690 $a 0607
710 2 $a Clark University. $3 212665
773 0 $t Dissertation Abstracts International $g 72-07B.
790 1 0 $a Landee, Christopher, $e advisor
790 $a 0048
791 $a Ph.D.
792 $a 2011
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3455151