Magnetocaloric features of complex molecular magnets: The (Cr_7Ni)_2 Cu molecular magnet and beyond

摘要

We study the new kind of systems represented by the Cr_7Ni-M-Cr_7Ni (M=Cu~(+2)) molecule, which is a promising molecular achievement from the perspective of molecular electronics. By using an effective quantum Hamiltonian, an exact calculation of the magnetic specific heat C_(Mag) and the magnetocaloric features, namely, the adiabatic change of the entropy △S_(Mag) and temperature △T_(ad), respectively, are developed. A systematic simulation of the magnetocaloric properties is generated by modifying the effective exchange couplings into the molecular system. Extended discussion of calculated magnetocaloric features and its possible realization by experimental methods, are performed. In addition, comparisons with an exact numerical result and with a Van Vleck transformation, which has important application in similar micromagnetic structures with no exact analytical solution and larger Hilbert space, are presented. Moreover, an expression for the entangling-excitation frequencies of these systems is given as first application of our simplified solution to the effective molecular Hamiltonian.