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Cu_3(tmen)_3(tma)_2(H_2O)_2 ·6.5H_2O - New S = 1/2 "Sawtooth" Chain?

100%

Vrábel P., Orendáčová A., Černák J., Orendáč M.

issue 5

993-994

The results of the investigation of magnetic susceptibility, magnetization and specific heat of Cu_3(tmen)_3(tma)_2(H_2O)_2·6.5H_2O (tmen = N,N,N',N'-tetramethylethane-1,2 diamine; H_3tma = 1,3,5-benzenetricarboxylic acid) are reported. The spatial arrangement of magnetic Cu(II) ions and network of covalent bonds suggest that the studied material might be a representative of S = 1/2 sawtooth chain with moderate exchange coupling J/k_{B}. The investigation of the temperature dependence of susceptibility and magnetic field dependence of magnetization yielding J/k_{B} ≈ - 0.63 K is consistent with the structural features. In addition, specific heat data reveal short-range correlations in milikelvin temperature range and indicate long-range ordering below 150 mK.

Experimental Studies of S=1 Heisenberg Planar Antiferromagnetic Chain Ni(C_{11}H_{10}N_{2}O)_{2}Ni(CN)_{4}

88%

Čizmár E., Černák J., Orendáč M., Herrmannsdörfer T., Feher A.

Acta Physica Polonica A

2000

vol. 97

issue 3

579-582

In this paper we discuss the results of experimental studies of specific heat and magnetic susceptibility of chain compound Ni(C_{11}H_{10}N_{2}O)_{2}Ni(CN)_{4}. We have observed a Schottky type anomaly at T=2.2 K in a temperature dependence of specific heat and the compound was identified as a S=1 Heisenberg antiferromagnetic chain with the subcritical exchange coupling D/k_{B}=5 K, D/|J|=5.2 and the strong in-plane anisotropy E/k_{B}=2.8 K. It has been found that the in-plane anisotropy affects the region of validity of a diluted exciton model [1] and a strong coupling model [2] for S=1 Heisenberg chains with the strong planar anisotropy. The analysis suggests that the in-plane anisotropy should be considered in any attempt to find a compound potentially located in the boundary of Haldane and "large-D" phases.

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2 Acta Physica Polonica A

1 2010

1 2000

2 Orendáč M.

2 Černák J.

1 Feher A.

1 Herrmannsdörfer T.

1 Orendáčová A.

1 Vrábel P.

1 Čizmár E.

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Cu_3(tmen)_3(tma)_2(H_2O)_2 ·6.5H_2O - New S = 1/2 "Sawtooth" Chain?

Experimental Studies of S=1 Heisenberg Planar Antiferromagnetic Chain Ni(C_{11}H_{10}N_{2}O)_{2}Ni(CN)_{4}