ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The magnetic behavior of NiCl2⋅H2O has been studied for the first time. A Curie–Weiss fit, χM=C/(T−θ), to the susceptibility between 90 and 300 K yields g=2.23±0.01(S=1) and θ=30.4±0.05 K. Systematic curvature in χ−1(T) is evident below 90 K. Despite the very positive θ, NiCl2⋅H2O appears to order antiferromagnetically at Tc=5.65±0.1 K, somewhat below a maximum in χ(T) at T(χmax)=8.4±0.1 K, with χmax=0.1297±0.0005 emu/mol. The ratios Tc/T(χmax)=0.67±0.01 and Tc/θ=0.186±0.005 suggest lower magnetic dimensionality, most likely one-dimensional character. Plausible looking fits to the low temperature susceptibility based on a one-dimensional antiferromagnetic Heisenberg model can be obtained. However, these presuppose antiferromagnetic intrachain exchange, and in NiCl2⋅H2O such exchange is almost certainly ferromagnetic, with weaker antiferromagnetic interchain interactions. Well above Tc the susceptibility can be accounted for assuming axial and rhombic crystal-field distortions, i.e., D[S(circumflex)z2−S(S+1)/3] and E[S(circumflex)x2−S(circumflex)y2] spin Hamiltonian terms, with exchange included in a mean field approximation. In the absence of single crystal data the parameters are only provisional, but clearly |D| and |E| are very large; the associated mean exchange interaction zJ/k=25.1 K is consistent with the observed θ value. Magnetization versus field isotherms exhibit an unusual evolution in shape with varying temperature; significant hysteresis is present even for temperatures somewhat above Tc. © 2000 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.372609
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