Multiscale phenomena in molecular matter

Magnetic properties of new molecular compounds based on single cobalt (II) ion

4 Jul 2017, 19:10

2h

poster presentation Molecular magnets and nanomagnets Poster Session

Speaker

Ms Magdalena Ceglarska (Institute of Physics, Jagiellonian University, prof. Stanisława Łojasiewicza 11, 30-348 Kraków, Poland)

Description

`Low-dimensional molecular magnets that show slow relaxation of magnetization are of interest because of their possible applications.$^{[1]}$ The smallest among those are Single Ion Magnets.$^{[2]}$ Based on cobalt salt, pyridine and 4-vinylpyridine, two new mononuclear compounds were synthesized: CoBr$_2$(py)$_2$ and CoBr$_2$(4vpy)$_2$. The measurements of AC susceptibility at temperatures below 5 K confirmed the occurrence of field-induced relaxation of magnetization for both. Based on Cole-Cole model fits to AC susceptibility vs. frequency, times of relaxation and energy barriers were determined: CoBr$_2$(py)$_2$ - $\tau_0=8\cdot 10^{-10}$ s, $\Delta/k_\mathrm{B}$ = 29(4) K, CoBr$_2$(4vpy)$_2$ - $\tau_0=1.4\cdot 10^{-11}$ s, $\Delta/k_\mathrm{B}$ = 35(7) K. The low values of the $\alpha$ parameter (below 0.3 for both compounds) confirmed that the measured compounds are indeed Single Ion Magnets. Despite the low values of $\tau _{0}$ and $\Delta/k_\mathrm{B}$, these compounds are very interesting because of one among the smallest sizes of the molecule (high density of magnetic centers per volume) and the possibilities to use other pyridine-based ligands to obtain other SIM compounds.` `This research was financed by the Polish National Science Centre within the SONATA Project UMO-2015/19/D/ST5/01936.` [1] Gatteschi D., Sessoli R., Villain J., `$\textit{Molecular Nanomagnets}$`, New York, Oxford University Press, 2006. [2] Frost J. M., Harriman K. L. M., Murugesu M., The raise of 3-d single-ion magnets in molecular magnetism: towards materials from molecules?, `$\textit{Chem. Sci.}$`, `$\textbf{7}$`, 2470 - 2491, 2016.