Analysis of the static magnetic field-dependent optical transmission of Ni nanorod colloidal suspensions
- Experimentalphysik, Universität des Saarlandes, Campus D2 2, D-66123 Saarbrücken (Germany)
The magnetic field-dependent optical transmission of dilute Ni nanorod aqueous suspensions was investigated. A series of four samples of nanorods were synthesized using the AAO template method and processed to stable colloids. The distributions of their length and diameter were characterized by analysis of TEM images and revealed average diameters of ∼25 nm and different lengths in the range of 60 nm–1100 nm. The collinear magnetic and optical anisotropy was studied by static field-dependent transmission measurements of linearly polarized light parallel and perpendicular to the magnetic field direction. The experimental results were modelled assuming the field-dependent orientation distribution function of a superparamagnetic ensemble for the uniaxial ferromagnetic nanorods in liquid dispersion and extinction cross sections for longitudinal and transversal optical polarization derived from different approaches, including the electrostatic approximation and the separation of variables method, both applied to spheroidal particles, as well as finite element method simulations of spheroids and capped cylindrical particles. The extinction cross sections were compared to reveal the differences associated with the approximations of homogeneous polarization and/or particle shape. The consequences of these approximations for the quantitative analysis of magnetic field-dependent optical transmission measurements were investigated and a reliable protocol derived. Furthermore, the changes in optical cross sections induced by electromagnetic interaction between two nanorods in parallel end-to-end and side-by-side configuration as a function of their separation were studied.
- OSTI ID:
- 22597780
- Journal Information:
- Journal of Applied Physics, Vol. 120, Issue 4; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
ANISOTROPY
APPROXIMATIONS
COLLOIDS
COMPARATIVE EVALUATIONS
CROSS SECTIONS
CYLINDRICAL CONFIGURATION
DISTRIBUTION FUNCTIONS
ELECTROMAGNETIC INTERACTIONS
FINITE ELEMENT METHOD
IMAGES
LENGTH
LIQUIDS
MAGNETIC FIELDS
NANOSTRUCTURES
NICKEL
PARTICLES
POLARIZATION
SUPERPARAMAGNETISM
SUSPENSIONS
TRANSMISSION ELECTRON MICROSCOPY