Phase transition between quantum and classical regimes for the escape rate of dimeric molecular nanomagnets in a staggered magnetic field
| Autor: | Owerre, Solomon Akaraka, Paranjape, M. B |
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| Rok vydání: | 2013 |
| Předmět: | |
| Zdroj: | Phys. Lett. A 378 (2014) 1407 |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1016/j.physleta.2014.03.019 |
| Popis: | We study the phase transition of the escape rate of exchange-coupled dimer of single-molecule magnets which are coupled either ferromagnetic ally or antiferromagnetically in a staggered magnetic field and an easy $z$-axis anisotropy. The Hamiltonian for this system has been used to study molecular dimer nanomagnets [Mn$_4$]$_2$. We generalize the method of mapping a single-molecule magnetic spin problem onto a quantum-mechanical particle to dimeric molecular nanomagnets. The problem is mapped to a single particle quantum-mechanical Hamiltonian in terms of the relative coordinate and a coordinate dependent reduced mass. It is shown that the presence of the external staggered magnetic field creates a phase boundary separating the first- from the second-order transition. With the set of parameters used by R. Tiron, $\textit{et al}$, \prl {\bf 91}, 227203 (2003), and S. Hill, $\textit{et al}$ science {\bf 302}, 1015 (2003) to fit experimental data for [Mn$_{4}$]$_2$ dimer we find that the critical temperature at the phase boundary is $T^{(c)}_0 =0.29K$. Therefore, thermally activated transitions should occur for temperatures greater than $T^{(c)}_0$. Comment: 9 pages, 6 figures. More elaborated than the published version |
| Databáze: | arXiv |
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