Study of the magnetic phase transition in a cyanide-bridged molecule-based material: [Mn(cyclam)][Fe(CN) 6]·3H 2O (cyclam=1,4,8,11-tetraazacyclotetradecane)

Abstract

Heat capacities of [Mn(cyclam)][Fe(CN) 6]·3H 2O (cyclam=1,4,8,11-tetraazacyclotetradecane) under zero magnetic field in the 0.1–300 K range were studied by adiabatic calorimetry. A heat capacity anomaly corresponding to the magnetic phase transition was detected at 6.2 K. The observed entropy gain (Δ S=2.32 R) is in good agreement with the theoretical magnetic entropy ( R ln 5×2=2.3 R) considering the spin multiplicity of high spin trivalent Mn and low spin trivalent Fe ions. Attempts have been made to interpret the low temperature heat capacity data in terms of the spin-wave theory. Possible magnetic interaction mechanism is discussed by comparing with those of related compounds. Heat capacity studies under applied magnetic fields indicated an antiferromagnetic to ferromagnetic transition. A field dependence study of magnetization at different temperatures revealed a field-induced metamagnetic transition.