Critical behavior of the Mn2[Nb(CN)8] molecular magnet

Abstract

Complementary experimental methods such as $\ensuremath{\mu}$SR spectroscopy, ac magnetometry, and relaxation calorimetry have been employed as a probe of critical behavior of a unique ferrimagnetic molecular magnet {[Mn${}^{\mathrm{II}}$(pydz)(H${}_{2}$O)${}_{2}$][Mn${}^{\mathrm{II}}$(H${}_{2}$O)${}_{2}$][Nb${}^{\mathrm{IV}}$(CN)${}_{8}$]$\ifmmode\cdot\else\textperiodcentered\fi{}$2H${}_{2}$O}${}_{n}$ with ${T}_{\mathrm{c}}\ensuremath{\approx}42$ K. A full set of critical exponents is determined. Static exponents $\ensuremath{\alpha}$, $\ensuremath{\beta}$, $\ensuremath{\gamma}$, and the dynamic exponent $w$ are extracted directly from the measurements. Further critical exponents $\ensuremath{\nu}$, $\ensuremath{\eta}$, and $z$ are derived on the basis of scaling or hyperscaling relations. The knowledge of the thermal dependence of the order parameter combined with the results of the calorimetric measurements allowed for the determination of two further static critical exponents $\ensuremath{\kappa}$ and ${\ensuremath{\kappa}}^{\ensuremath{'}}$. The system shows a close affinity to the three-dimensional (3D) Heisenberg model. Ferrimagnetism of the compound leads to a coexistence of typically ferro- and antiferromagnetic characteristics.