Speaker
Prof.
Motohiro Nakano
(Osaka University)
Description
`The octahedral manganese(III) complex, [Mn$^\mathrm{III}$(taa)] (H$_3$taa = tris(1-(2-azolyl)-2-azabuten-4-yl)amine), has long been known as a rare example of (3d)$^4$ spin-crossover system, having a steep spin-crossover phase transition at $T_\mathrm{c}$ = 48 K between a high-spin $^5$E$_g$ and a low-spin $^3$T$_{2g}$ states [1, 2]. Since the high-spin state is obviously subject to the Jahn-Teller effect, the electronic states are coupled with lower-symmetry deformation modes lifting $^5$E$_g$ orbital degeneracy in addition to a symmetrical breathing mode responsible for the spin crossover. This simultaneous involvement of two molecular bistabilities may afford a variety of condensed states (phases) due to competitive or cooperative interactions [3]. The phase diagram and the phase transition behavior were thoroughly explored via several probes, including dielectric measurements [4], magnetization under pulsed high field [5], HF-EPR [6], and magnetic susceptibility measurements using high-pressure clamp cell [7]. All the results were successfully interpreted in a unified fashion based on a four-state Ising-Potts model with mean-field approximation.`
References
[1] P. G. Sim and E. Sinn, `$\textit{J. Am. Chem. Soc.}$` `$\textbf{103}$`, 241 (1981). DOI: 10.1021/ja00391a067.
[2] Y. Garcia, O. Kahn, J.-P. Ader, A. Buzdin, Y. Meurdesoif, and M. Guillot, `$\textit{Phys. Lett. A}$` `$\textbf{271}$`, 145 (2000). DOI: 10.1016/S0375-9601(00)00346-7.
[3] M. Nakano, G. Matsubayashi, and T. Matsuo, `$\textit{Adv. Quantum Chem.}$` `$\textbf{44}$`, 617 (2003). DOI: 10.1016/S0065-3276(03)44041-0.
[4] M. Nakano, G. Matsubayashi, and T. Matsuo, `$\textit{Phys. Rev. B}$` `$\textbf{66}$`, 212412 (2002). DOI: 10.1103/PhysRevB.66.212412.
[5] S. Kimura, Y. Narumi, K. Kindo, M. Nakano, and G. Matsubayashi, `$\textit{Phys. Rev. B}$` `$\textbf{72}$`, 064448 (2005). DOI: 10.1103/PhysRevB.72.064448.
[6] S. Kimura, T. Otani, Y. Narumi, K. Kindo, M. Nakano, and G. Matsubayashi, `$\textit{J. Magn. Magn. Mater.}$` `$\textbf{272-276}$`, 1102 (2004). DOI: 10.1016/j.jmmm.2003.12.1334; S. Kimura, M. Hagiwara, Y. Narumi, M. Nakano, and K. Kindo, `$\textit{J. Phys.: Conf. Ser.}$` `$\textbf{200}$`, 022025 (2010). DOI: 10.1088/1742-6596/200/2/022025.
[7] M. Nakano, `$\textit{Bull. Jpn. Soc. Coord. Chem.}$` `$\textbf{58}$`, 6 (2011). DOI:10.4019/bjscc.58.6.
Primary author
Prof.
Motohiro Nakano
(Osaka University)
