Simultaneous Study of Brownian and Néel Relaxation Phenomena in Ferrofluids by Mössbauer Spectroscopy

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• 作者：J. Landers ; S. Salamon ; H. Remmer ; F. Ludwig ; H. Wende
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：February 10, 2016
• 年：2016
• 卷：16
• 期：2
• 页码：1150-1155
• 全文大小：471K
• ISSN：1530-6992

文摘

We demonstrate the ability of M?ssbauer spectroscopy to simultaneously investigate Brownian motion and Néel relaxation in ferrofluidic samples. For this purpose, M?ssbauer spectra of coated iron oxide nanoparticles with core diameters of 6.0–26.4 nm dissolved in 70 vol % glycerol solution were recorded in the temperature range of 234–287 K and compared to low-temperature spectra without Brownian motion. By comparison to theory, we were able to determine the particle coating thickness and the dynamic viscosity of the fluid from the broadening of the absorption lines (Brownian motion), as well as the state of Néel relaxation. Results from M?ssbauer spectroscopy were crosschecked by AC-susceptometry at several temperatures for Brownian motion and in the high-frequency regime (100 Hz–1 MHz) for Néel relaxation.