Imperial College London
Alternate

Professor Mike Robb, FRS

Faculty of Natural Sciences, Department of Chemistry

Chair in Chemistry
 
 
 
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Contact

 

+44 (0)20 7594 5757mike.robb Website

 
 
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Location

 

301cMolecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Citation

BibTex format

@article{Jornet-Somoza:2018:10.1021/acs.jpca.7b10657,
author = {Jornet-Somoza, J and Deumal, M and Borge, J and Robb, MA},
doi = {10.1021/acs.jpca.7b10657},
journal = {Journal of Physical Chemistry A},
pages = {2168--2177},
title = {A definition of the magnetic transition temperature using valence bond theory},
url = {http://dx.doi.org/10.1021/acs.jpca.7b10657},
volume = {122},
year = {2018}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Macroscopic magnetic properties are analyzed using Valence Bond theory. Commonly the critical temperature TC for magnetic systems is associated with a maximum in the energy-based heat capacity Cp(T). Here a more broadly applicable definition of the magnetic transition temperature TC is described using spin moment expectation value (i.e. applying the spin exchange density operator) instead of energy. Namely, the magnetic capacity Cs(T) reflects variation in the spin multiplicity as a function of temperature, which is shown to be related to ∂[χT(T)]/∂T. Magnetic capacity Cs(T) depends on long-range spin interactions that are not relevant in the energy-based heat capacity Cp(T). Differences between Cs(T) and Cp(T) are shown to be due to spin order/disorder within the crystal, that can be monitored via a Valence Bond analysis of the corresponding magnetic wavefunction. Indeed the concept of the Boltzmann spin-alignment order is used to provide information about the spin correlation between magnetic units. As a final illustration, the critical temperature is derived from the magnetic capacity for several molecular magnets presenting different magnetic topolo- gies that have been experimentally studied. A systematic shift between the transition temperatures associated with Cs(T) and Cp(T) is observed. It is demonstrated that this shift can be attributed to the loss of long-range spin correlation. This suggests that the magnetic capacity Cs(T) can be used as a predictive tool for the magnetic topology, and thus for the synthetic chemists.
AU  - Jornet-Somoza,J
AU  - Deumal,M
AU  - Borge,J
AU  - Robb,MA
DO  - 10.1021/acs.jpca.7b10657
EP  - 2177
PY  - 2018///
SN  - 1089-5639
SP  - 2168
TI  - A definition of the magnetic transition temperature using valence bond theory
T2  - Journal of Physical Chemistry A
UR  - http://dx.doi.org/10.1021/acs.jpca.7b10657
UR  - http://hdl.handle.net/10044/1/56774
VL  - 122
ER  -
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