Dynamics of field-induced ordering in magnetic colloids studied by new time-resolved small-angle neutron-scattering techniques.
Dynamics of field-induced ordering in magnetic colloids studied by new time-resolved small-angle neutron-scattering techniques.
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通过新的时间分辨小角中子散射技术研究磁性胶体中场致有序的动力学。
DOI：
10.1103/physrevlett.97.057202
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发表时间：
2006
影响因子：
8.6
通讯作者：
R. Gähler
中科院分区：
文献类型：
--
作者：
Albrecht Wiedenmann;U. Keiderling;K. Habicht;M. Russina;R. Gähler
采用新的时间分辨频闪小角中子散射技术，在振荡磁场中监测了浓Co磁流体中纳米颗粒磁矩的反转。在微米范围内的时间分辨率是通过使用脉冲束技术，TISANE，而在连续模式分辨率是有限的波长扩展到约1毫秒。各向异性散射图案的频率依赖性已建模使用朗之万动力学。动力学遵循两步机制：场诱导有序由纳米颗粒的快速布朗旋转控制，特征时间约为160 μ s。通过布朗旋转或Néel型磁矩旋转，尺寸约为100 nm的局部有序畴的磁弛豫在几秒钟内发生。
The reversal of magnetic moments of nanoparticles in concentrated Co ferrofluids was monitored in an oscillating magnetic field by new time-resolved stroboscopic small-angle neutron-scattering techniques. Time resolution in the micros range was achieved by using a pulsed beam technique, TISANE, while in continuous mode resolution was limited by the wavelength spread to about 1 ms. The frequency dependence of anisotropic scattering patterns has been modeled using Langevin dynamics. The dynamics follows a two step mechanism: field-induced ordering is governed by fast Brownian rotation of nanoparticles with a characteristic time of about 160 micros. Magnetic relaxation of locally ordered domains of about 100 nm in size takes place within a few seconds by Brownian rotation or by Néel type rotation of magnetic moments.