Ferrimagnetic properties in Fe^II–III (oxy)hydroxycarbonate green rusts

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• 作者：Benoî ; t Rusch ; Jean-Marie R. Gé ; nin ; Christian Ruby ; Mustapha Abdelmoula ; Pierre Bonville
• 关键词：Hydroxycarbonate ; Green rust ; Oxyhydroxycarbonate ; Mö ; ssbauer spectroscopy ; Susceptibility ; Magnetic ordering ; Ferrimagnetism ; Fougerite
• 刊名：Solid State Sciences
• 出版年：2008
• 出版时间：January 2008
• 年：2008
• 卷：10
• 期：1
• 页码：40-49
• 全文大小：1854 K

文摘

A ferrimagnetic behaviour is observed in green rust GR(CO₃²⁻), the layered double hydroxide Fe^II–III hydroxycarbonate Fe^II₄Fe^III₂(OH)₁₂CO₃, by using Mössbauer spectroscopy and susceptibility measurements. Moments lying within two-dimensional cation layers are parallel for same species and antiparallel between Fe^II and Fe^III that lead to two magnetic ordering temperatures, 5.2 and 7 K, respectively. Mössbauer spectrum shows at 1.4 K a sextet with field distribution from 350 to 580 kOe for ferric ions, and an octet reflecting a mixture of states with field of 130 kOe and quadrupole splitting of −3.0 mm s⁻¹ for ferrous ions. Ferric oxyhydroxycarbonate GR(CO₃²⁻)^*, Fe^III₆O₁₂H₈CO₃, displays at 4 K a sextet with field distribution between 400 and 500 kOe. Transition is at around 80 K. Spectra of deprotonated GR(CO₃²⁻)^* at a ferric molar fraction x = 0.88 display a ferric sextet behaving similarly with transition at around 70 K and two paramagnetic doublets, one ferrous and one ferric that remain at 4.2 K. This suggests that the deprotonation of GR(CO₃²⁻) gives magnetic domains of definite compositions at x = 1/3, 2/3 and 1 and long range order of Fe^III ions along a translation a × √3 if a is the parameter of the cation hexagonal pavement is confirmed.