Advanced Materials Chemistry
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Advanced Materials Chemistry
Magnetic Materials – J.P. Attfield
In-course assessment – Level 10 (undergraduate students)
This exercise is based around the research paper below and will require concepts from the lectures and some independent reading around to answer the questions. If you are unable to access the paper online then please ask the CTO Course Secretary for a copy.
Designed Ferromagnetic, Ferroelectric Bi2NiMnO6
Masaki Azuma et al, J. AM. CHEM. SOC. 2005, 127, 8889-8892.
https://doi.org/10.1021/ja0512576
The marks for each part are indicated as [x]. In total your answers to all questions in this exercise should be less than 1000 words. Answers should be submitted as a PDF. You may insert diagrams but only ifyou have drawn them yourself. You do not need citations to the literature or other sources of information in your answers.
Answer all of the following parts.
(a) Bi2NiMnO6 was designed to be a ferroelectric and ferromagnetic material.
Describe briefly what a ferroelectric is. Explain which of the metals Bi, Ni, and Mn
contribute to each of these properties and why. [5]
(b) Use the inverse susceptibility data in Fig. 3(a) to calculate the effective
paramagnetic moment µeff per mol of Bi2NiMnO6. [Information; the constant A in the Curie equation M/H =Aµeff2/T has value A = 0.1246 for the units shown in the plot.] [3]
(c) Alternative charge configurations for Bi2NiMnO6 could be Bi2Ni2+Mn4+O6 or Bi2Ni3+Mn3+O6. Calculate the effective paramagnetic moments and the saturated ferromagnetic moments per mol of Bi2NiMnO6 for these charge configurations and compare them to the experimental values from part (b) and from Fig 3(b). [4]
(d) Use your answers from part (c) and other data presented in the paper to give a critical assessment of how the charge distribution was assigned to be Bi2Ni2+Mn4+O6. [5]
(e) Explain using an orbital diagram why ferromagnetic superexchange is
predicted for the Ni2+-O- Mn4+ interactions in Bi2 NiMnO6. [3]
2023-03-05