Download Document

Investigation of Magneto-optical Linear Dichroism Property of the TMA Coated Magnetic
Fluid
S.O.Köklü1, I.Yarici*1,Y.Oztürk1
1
Ege University, Bornova, 35100 Izmir, Turkey
(Received 01 March 2015; revised manuscript received 251 May 20143; published online 22 August 2015)
In this study magneto-optical linear dichroism (MOLD) effects of the Tetramethylammonium hydroxide (TMA) coated magnetic fluid was investigated. In our study MOLD and optical absorbtion properties of
produced magnetic nanoparticles were investigated at the wavelength range of 550-900 nm. For this purpose MOLD measurement system was designed. External magnetic field applied up to 400G during the
MOLD measurement. TMA coated magnetic nanoparticles produced by co-precipitation method at room
temperature in nitrogen atmosphere. The magnetic, structural and size properties of the particles were
measured using X-ray diffractometer (XRD), dynamic light scattering (DLS) and vibrating sample magnetometer (VSM). The saturation magnetization (Ms) of produced Fe3O4 was determined as 62 emu/g and the
average particle size was 34nm. It was observed that with the increase of absorption, the MOLD effect was
getting increased
Keywords: Magnetic Fluid,Linear Dicroishm, Nanoparticle.
1. INTRODUCTION
Magnetic fluids consist of magnetic particles with the
varying sizes between 1 to 500 nm are dispersed in a
liquid carrier. Ferrofluid give respond to the applied
external magnetic field. This means the position of the
liquid can be vary as desired with the applied external
magnetic field [1]. Magnetic fluids have both flow properties of liquids and magnetic properties of solids. Magnetic particles mainly consists of carrier liquid and surfactant. Magnetic fluids are used in many technological
applications and these applications are constantly on the
rise [2-4]. Although the magnetic fluids are isotropic ;
with the applied external magnetic field they show
anisotropic characteristic and exhibit magneto- optic
effects like Faraday rotation, birefringence and so on.
The magnetic particles may lead to agglomeration. In
order to prevent the agglomeration, magnetic particles
should be covered with a surface active material.
Magneto-optical effect of the magnetic fluid, as a result of the physical and magnetic properties of nanoparticles in the suspension, studied by Kerr (1901) , Majorana (1903) and Cotton - Mouton (1907). The optical
effects of magnetic fluids, linear absorption and linear
birefrigence have been studied since 1960. Such interactions under magnetic field are called magneto-optic
effect. In case of transmission from the material, this
magneto-optical effects are linear dichroism, circular
dichroism, linear birefringence and circular birefringence [5]. In a magnetic liquid some clusters are formed
aligned the applied magnetic field. And this formation
has lead to a strong magneto-optical effect. It may show
some linear formations occur due to the static magnetic
forces between them. Every particle in the electric field
under this cluster is considered to be oscillating dipoles.
These dipoles interact to each other because of their
closeness. This interaction is asymmetrical depending
on the direction of the light beam. This asymmetry
creates the optical anisotropy effect that lead to linear
dicroishm and linear birefringence effect in the magnetic fluid [5].
Polarization refers to the orientation of the electric
field vectors. If the electric field points are in a fixed
orientation, as a special case it gives the linearlypolarized wave. If the wave vector components are polarized in different phases and have equal amplitude, they
generate circularly polarized waves. Similarly, the polarized waves in different phase and different amplitude
give elliptical polarized waves [5]. Polarization at any
point is expressed by the sum of the wave vector components by the principle of superposition [6].
Light passes through the magnetic fluid with less interaction and absorption, when the polarization direction
is perpendicular to the magnetic field. On the other
hand, when the polarization direction parallel to the
applied magnetic field, light absorption increases as
electric dipole of aligned nano-particles and electromagnetic field interacts.
In this study nanoparticles to be used in magnetic
fluid were produced by using co-precipitation method.
The macro dimensions particles in all synthesized magnetic nanoparticles were separated by centrifugation.
The magnetic, structural and size properties of the particles were measured using X-ray diffractometer (XRD),
dynamic light scattering (DLS) and vibrating sample
magnetometer (VSM). The optical transmission and
linear dichroism measurements of produced magnetic
fluids are taken by using the designed magneto-optical
experimental set-up.
2. EXPERIMENTAL
In present study, briefly, FeCl3.6H2O was dissolved
in deionized water and FeCl2.4H2O was dissolved in 1M
HCl. The iron solutions (Fe+2/Fe+3) were added into the
same flask with molar ratio 1:2 and mixed with magnetic stirrer in nitrogen atmosphere for 30 minutes. After
this mixing procedure, ammonium hydroxide was added
with peristaltic pump up to the reaching 10 as pH value.
The resulted particles were separated magnetically and
washed several times with 5% M NH4OH-water solution.
The precipitated magnetic particles coated with TMA in
pure water. The magnetic, structural and size properties
of the particles were measured using X-ray diffractometer, dynamic light scattering and vibrating sample magnetometer.
A broadband (550-900nm) magneto-optical measurement system was designed to examine optical transmission of parallel and perpendicular polarization after
passing through the magnetic liquid under applied field .
In this system tungsten lamp used as a unpolarized light
source. Polarizer used to polarize the light parallel (P0)
and perpendicular (P90) to the applied magnetic field
axis. After the interaction of the polarized light with the
material, the transmitted light was detected by a spectrometer. The applied magnetic field produced by the
electromagnet with variable current source.
Fig 1-The designed magneto-optical measurement system
produced magnetic particle size and standard deviation
are 34 nm and 17 nm respectively.
For the magnetic analysis of nanoparticles
Lakeshore 736, 7400 VSM device was used. The measurements show that the coercivity of samples are low
and particles behave like super paramagnetic material.
The saturation magnetization of our sample was measured as 62 emu/g. It is known that for macro size bulk
Fe3O4 the saturation magnetization is 93 emu/g [5].
Generally the saturation magnetization of nanoparticles
is lower than bulk ones. One reason of this is the negative effect of nonmagnetic shield on the particles [5].
The optical transmission measurements for magnetic
liquid prepared with TMA and ethanol is shown in Fig.3.
It can be seen that under magnetic field transmitted
light intensity is different for perpendicular to the applied magnetic field (P90) and parallel to the applied
magnetic field (P0) cases. So the magneto-optic linear
dichroism effect is seen clearly. This effect in a number
of studies on this issue is explained by the created chain
structure of particles under magnetic field [6]. Interactions between the magnetic nanoparticles that form the
chain structure and electric dipole cause different absorption values.
The variation of transmitted light is investigated
for the magnetic fluids have different absorption values
(0.5, 1.5 and 2.5 at 550 nm) under varying magnetic
field. Measurements are taken for both P0 and P90
polarization cases.
The light transmission from the magnetic liquid
measured by the spectrometer between the range of 5501000nm depending on polarization direction and magnetic field intensity.
3.
RESULTS AND DISCUSSION
The structural analysis of the produced magnetic nanoparticles was done using Philips Expert 1830 X-ray
diffractometer. Phase information about the magnetic
nanoparticle is given in the Fig.2. These phase values
have orientations (220), (311), (400), (511) and (440)
respectively. Figure XX shows that the located phases
belongs to Fe3O4
Fig.2-X- ray diffraction pattern of magnetic nanoparticles
The sizes and distributions of the magnetic nanoparticles in the solution were determined using Zetasizer 4
Nano S-Malvern DLS. According to the DLS results, the
Fig.3-The variation of transmitted light for the magnetic fluid
absorption values 0.5, 1.5 and 2.5 at 550nm
When magnetic field applied to the magnetic fluid,
between nanoparticles some shapes are occurs through
magnetic forces caused by the magnetic field. These
formations are formed as the chain-like structures. The
formations of these structures influence the quantity of
transmitted light. With the increasing magnetic field
strength, more particles are involved in the formation of
the chain structure and the dispersed nanoparticles are
passed regular structures. Chain-like structures have
the same orientation with the applied magnetic field, so
measurements taken in the parallel and perpendicular
polarization to the magnetic field direction are affected
by this structure. In case of the polarization direction is
perpendicular to the magnetic field, light transmit
through the magnetic fluid without being affected by
chain structure. As a result, it is observed that amount
of the transmitted light was increased in the P90 case.
Fig.4- The optical transmittance change dependent wavelength
for the absorption value 0.5 at 550 nm for P0 and P90 cases.
Fig.6-The optical transmittance change dependent wavelength
for the absorption value 2.5 at 550 nm for P0 and P90 cases.
4. CONCLUSION
TMA coated magnetic nanoparticles produced by coprecipitation method at room temperature in nitrogen
atmosphere. XRD patterns indicate that magnetic nanoparticles have Fe3O4 phases. Magnetic properties were
observed, and the saturation magnetization (Ms) of produced Fe3O4 was determined as 62 emu/g. The average
particle was measured by DLS and found as 34nm. The
MOLD effects of the TMA coated magnetic fluid was
investigated for the absorption values 0.5, 1.5 and 2.5.
Measurements are taken for both P0 and P90 polarization cases. When magnetic field applied to the magnetic
fluid, between nanoparticles some shapes are occurs. It
was observed that with the increase of absorption, the
MOLD effect was getting increased.
Fig.Error! No text of specified style in document.-The optical
transmittance change dependent wavelength for the absorption
value 1.5 at 550 nm for P0 and P90 cases.
REFERENCES
1. Mehta, R.,Optical Materials, 1436–1442p. (2013).
2. Ge J. ve H. Y.,Angew. Chem., Int. Ed., 46 (23), 4342–
4345p. (2007a)
3. Ge J. ve H. Y., Angew. Chem. Int. Ed. 46, 7428 –
7431p. (2007b).
4. M Shalaby, M Peccianti, Y Ozturk, M Clerici, I AlNaib, L Razzari, T Ozaki, Applied Physics Letters 100 (24),
241107, (2012)
5. M. Xu and P. J. Ridler, J. Appl. Phys. 82, 326 (1997)
6. Blair, C., & Coleman, J.Optics. PY2004.,(2004).