Observation of thermodynamics originating from a mixed-spin ferromagnetic chain
Hironori Yamaguchi, Shunsuke C. Furuya, Satoshi Morota, Seiya Shimono, Takashi Kawakami, Yuka Kusanose, Y. Shimura, Kiichi Nakano, Yuko Hosokoshi
Abstract
We present a model compound that forms a mixed-spin ferromagnetic chain. Our material design, based on the organic radicals, affords a verdazyl-based complex $(p\text{\ensuremath{-}}\mathrm{Py}\text{\ensuremath{-}}{\mathrm{V})}_{2}[\mathrm{Mn}{(\mathrm{hfac})}_{2}]$. The molecular orbital calculations of the compound indicate the formation of a mixed-spin-(1/2, 1/2, 5/2) ferromagnetic chain. The temperature dependence of magnetic susceptibility reveals its ferromagnetic behavior. The magnetic specific heat exhibits a double-peak structure and indicates a phase transition at the low-temperature peak. The observed characteristics are explained using the quantum Monte Carlo calculations. Furthermore, the modified spin-wave theory verifies that the double-peak structure of the specific heat significantly reflects the relative ration of the acoustic excitation band and the optical excitation gap.