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

We have investigated the magnetic properties of two-dimensional networked single-molecule magnet, [Mn₄(hmp)₄Br₂(OMe)₂(dcn)₂]·0.5H₂O·2THF (Hmp=2-hydroxymethylpyridine, dcn=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 (T_B) in low frequency limit is estimated to be 2.00 K at ambient pressure. As pressure increases, the T_B 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 T_B, 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.