Self-Adjusted Traveling Solvent Floating Zone Growth of Single Crystal CaFe2O4

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• 作者：Rajasree Das ; Sunil Karna ; Yen-Chung Lai ; Fang-Cheng Chou
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：January 6, 2016
• 年：2016
• 卷：16
• 期：1
• 页码：499-503
• 全文大小：381K
• ISSN：1528-7505

文摘

Single crystals of high-quality CaFe₂O₄ have been grown successfully using a self-adjusted traveling solvent floating zone method with a four-mirror optical furnace in oxygen atmosphere. Although CaFe₂O₄ has been reported to melt incongruently, the optimal molten zone has been achieved through a self-adjusted cooling following the liquidus line directly using the stoichiometric CaFe₂O₄ as both the feed and flux rods in the beginning. Details regarding long-term stability of the molten zone and lamp power optimization to obtain the bubble-free molten zone are discussed. The obtained large single crystal of a few centimeters long and ～0.5 cm in diameter shows homogeneous stoichiometry and crystallinity as verified by the optical microscopy and synchrotron X-ray diffraction structure refinement. Long range ferrimagnetic spin ordering of T_N ≈ 180 K is confirmed from the measurement of magnetization as a function of temperature, which shows significant thermal hysteresis and field dependence. Curie–Weiss law fitting of homogeneous susceptibility data above T_N in the paramagnetic regime suggests that the localized spins of Fe³⁺ are close to the high spin state of d⁵ with S = 5/2 in an octahedral crystal field, and the negative Weiss temperature of Θ ≈ ?115 K is consistent to a ferrimagnetic ground state of antiferromagnetically ordered spins in unequal size.