Thermodynamic investigation of coordination-networked systems of[Mn4] single-molecule magnets under pressure

Abstract

Low temperature heat capacity measurements under pressure were performed for tinysingle crystals of two-dimensional coordination-networked compounds consisting of[Mn4] single-molecule magnets (SMMs) by the ac temperature modulation technique.Systematic variations of the peak temperature and the peak width of thethermal anomalies produced by pressure were clearly detected using tworuthenium oxide resistance chips in the Cu–Be clamp-type cell. A linearincrease of the Néel temperature for an ordering set of large SMM spins withS = 9 wasobserved in [Mn4(hmp)6{N(CN)2}2](ClO4)2, while a non-monotonic variation of the peak temperatures and peak shapes was observed in[Mn4(hmp)4Br2(OMe)2{N(CN)2}2](ClO4)2·2THF·0.5H2O (hmp− = 2-hydroxymethylpyridinate;N(CN)2− = dicyanamide as the linker among SMMs). We also report on thermodynamic behavior produced bychanging external pressures and magnetic fields. The results are discussed in terms of thetilting angle of Ising axes in the two-dimensional plane.