Pressure effects on Mn4 single-molecule magnet with two-dimensional correlation

We have investigated the magnetic properties of two-dimensional networked single-molecule magnet, [Mn-4(hmp)(4)Br-2 (OMe)(2)(dcn)(2)]center dot 0.5H(2)O center dot 2THF (Hmp = 2-hydroxymethylpyridine, den = dicyanamide, THF = tetrahydrofuran), through the AC susceptibility measurements up to P = 15.3 kbar. This compound exhibits superparamagnetic relaxation phenomenon below 3 K, and the blocking temperature (TB) in low frequency limit is estimated to be 2.00 K at ambient pressure. As pressure increases, the TB once decreases and, at around P = 3 kbar, it turns to increase. At P = 15.3 kbar, the T-B reaches 2.27 K. By analyzing the frequency dependence of TB, it has been revealed that a dynamical critical exponent of the power-law fitting shows the change of up and down, and it approaches 2.0 at last. This result suggests that the intercluster magnetic network changes by pressurization and finally a conventional phase transition may be realized. (c) 2006 Elsevier B.V. All rights reserved.