Specific heat of spin ladder lanthanide and transition-metal-based molecular magnets

摘要

The compounds Ln_2[Cu(opba)]_3·S (where opba stands for ortho-phenylenebis(oxamato) and S for solvent molecules) with Ln = Tb. Dy. Ho are spinladder molecular magnets. Specific heat measurements down to 0.1 K show that these compounds undergo three-dimensional magnetic ordering, with T_C = 0.81 K and T_C = 0.74 K for the Tb- and the Dy-containing compounds, respectively. For the Ho-containing compound, only the high temperature tail of the #lambda# anomaly is detected by a specific heat measurement. In combination with a low-temperature suceptibility measurement (not presented here), it can be concluded that its ordering temperature is between 0.05 and 0.1 K. These results are compared with the magnetic propeties of the isostructural compound Gd_2[Cu(opba)]_3·S, which is a ferromagnet.