title: Effect of nonmagnetic substitution on the magnetic properties and charge-transfer phase transition of an iron mixed-valence complex, (n-C3H7)4N[Fe(II)Fe(III)(dto)3] (dto = C2O2S2).
abstract: The iron mixed-valence complex (n-C(3)H(7))(4)N[Fe(II)Fe(III)(dto)(3)] exhibits a novel type of phase transition called charge-transfer phase transition (CTPT), where the thermally induced electron transfer between Fe(II) and Fe(III) occurs reversibly at ~120 K, in addition to the ferromagnetic phase transition at T(C) = 7 K. To investigate the mechanism of the CTPT, we have synthesized a series of magnetically diluted complexes (n-C(3)H(7))(4)N[Fe(II)(1-x)Zn(II)(x)Fe(III)(dto)(3)] (dto = C(2)O(2)S(2); x = 0-1), and carried out magnetic susceptibility and dielectric constant measurements and (57)Fe Mössbauer spectroscopy. With increasing Zn(II) concentration (x), the CTPT is gradually suppressed and disappears at x ≈ 0.13. On the other hand, the ferromagnetic transition temperature (T(C)) is initially enhanced from 7 K to 12 K between x = 0.00 and 0.05, despite the nonmagnetic nature of Zn(II) ions, and then it decreases monotonically from 12 K to 3 K with increasing Zn(II) concentration. This anomalous dependence of T(C) on Zn(II) concentration is related to a change in the spin configuration of the ferromagnetic state caused by the partial suppression of the CTPT.
authors.affiliation: Department of Chemical Science and Technology, Graduate School of Chemical Science and Technology, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan.
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Ida
authors.forename: Atsushi
authors.initials: A
authors.lastname: Okazawa
authors.forename: Norimichi
authors.initials: N
authors.lastname: Kojima
authors.forename: Ryo
authors.initials: R
authors.lastname: Shimizu
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yamada
authors.forename: Masaya
authors.initials: M
authors.lastname: Enomoto