A The Field-induced Effect of Light Transmission for FeOOH-ZnFe2O4 Ferrofluids Control
TELKOMNIKA, Vol.14, No.3A, September 2016, pp. 306~312
ISSN: 1693-6930, accredited A by DIKTI, Decree No: 58/DIKTI/Kep/2013
DOI: 10.12928/TELKOMNIKA.v14i3A.4438
306
The Field-Induced Effect of Light Transmission for
FeOOH-ZnFe2O4 Ferrofluids Control
Anrong Wang*1, Pengzhi Wei2, Yufeng Shao3, Xiangfei Nie4, Kezhong Liang5, Haiyan
Huang6
1,3,4,5,6
Key Laboratory of Signal and Information Processing, Chongqing Three Gorges University,
Wanzhou District, Chongqing, 404100, P. R. China
2
College of Science, Harbin Engineering University, Nangang District, Harbin, 150006, P. R. China
*Corresponding author, e-mail: [email protected]
Abstract
The paper is supposed to find the change of the light transmission rate with the change of time of
the same volume fraction of ZnFe2O4 ferrofluids, FeOOH ferrofluids and FeOOH-ZnFe2O4 binary
ferrofluids, applied in different magnetic field, in parallel to the light direction. The field-induced effects of
light transmission for the three ferrofluids are compared, so as to explore the reason from the
microstructure change of the ferrofluids.
Keywords: Ferrofluids, magnetic field, light transmission, field-induced effect
Copyright © 2016 Universitas Ahmad Dahlan. All rights reserved.
1. Introduction
Ferrofluids refer to the colloidal suspensions dispersed of the strong magnetic
nanoparticles in certain carried liquid. Applied in the magnetic field, magnetic particles form a
chain, orderly arrange along the direction of the magnetic field, creating optical anisotropy.
Researches have been carried out on light transmission change and resilience of magnetic
nanoparticles under the effect of the magnetic field [1-3]. Based on that [4], the paper is to make
a comparison of the field-induced effect of light transmission for weak magnetic ZnFe2O4
ferrofluids, FeOOH ferrofluids and FeOOH-ZnFe2O4 binary ferrofluids, as well as to present the
rule and mechanism of the field-deduced light transmission.
2. Materials and Methods
2.1. The Preparation of Samples
The ZnFe2O4 and α-FeOOH nanoparticles are produced by chemical co-precipitation
technology with FeCl3, ZnCl2, NaOH, HCl, and HNO3. Then Q = 0.04, v=0.4% FeOOH of ionic
ferrofluid and Q = 0.04, v=0.4% ionic ferrofluid are synthesized, in the end, FeOOH mixed with
magnetic liquid ZnFe2O4 as FeOOH-ZnFe2O4 dual magnetic liquid. The FeOOH-ZnFe2O4 binary
ferrofluids are obtained by mixing both the ferrofluids.
The samples are ZnFe2O4 ferrofluids, FeOOH ferrofluids and FeOOH-ZnFe2O4 binary
ferrofluids, in the flat glass case, made into (15mm×15mm×0.53mm) film-like light transmission
samples.
2.2. Experimental Apparatus Figure of Field-Deduced Light Transmission
As shown in Figure 1, a laser beam L produced by He-Ne laser irradiate spectroscope
b, divided into two beams of light L1 and L2. Beams L1 go through the magnetic field (sample)
with e1 magnetic liquids in, then pass the adjustable polarizer c1, and expose to the silicon
photocell f1. Beam L2 directly go through the magnetic liquid e2 (sample for reference), then
pass the adjustable polarizer C2, and expose to the silicon photocell f2. Silicon photocell f1 and f2
convert the light signal strength of L1 and L2, respectively, for the current intensity, which are
input and analyzed by the computer, to get the intensity of laser beams L1 and L2. The values of
intensity of the I1, I2, are marked by silicon photocell electrical signal (mV for intensity value). To
Received March 27, 2016; Revised July 22, 2016; Accepted August 3, 2016
307
ISSN: 1693-6930
measure light transmission, one need to adjust adjustable polarizer light L1 and L2 until equal
light intensity values is reached. The beam intensity ratio η＝I1/I2 is defined as light
transmittance, namely relative transmittance of light. Without magnetic field, the relative light
transmittance is 1, with magnetic field, the relative light transmittance can tell the influence of
field-deduced light transmission for the ferrofluids. At room temperature, the effect of fielddeduced light transmission for samples ZnFe2O4 ferrofluids, FeOOH ferrofluids and FeOOHZnFe2O4 binary ferrofluids are measured, the corresponding mechanism are analyzed
theoretically.
Figure 1. The sketch map of experimental device
3. Results
3.1. The TEM and VSM Measure of ZnFe2O4 and α-FeOOH Nanoparticles
Figure Figure 2(a) and Figure 2(b) are the TEM and VSM test chart of ZnFe2O4 and αFeOOH nanoparticles. From the figure both are ball-shaped. Size distribution of the
nanoparticles, produced by chemical co-precipitation technology, is lognormal distributed.
d
d ln x
g
(ln x ln x g )
1
exp[
]
2 ln 2 g
2 ln g
2
(1)
x
Where x the diameter of the nanoparticles, g is the geometric average particle size,
is the geometric standard deviation of size distribution. So 4.22nm and 8.16nm are the
geometric average particle sizes of ZnFe2O4 nanoparticles and α-FeOOH nanoparticles, 0.26 is
the geometric deviations.
As ZnFe2O4 is weak magnetic, its magnetization curve is linear, the initial susceptibility
1/ 2
i (dM / dH ) H 0 0 mM s / 3k BT [5], of which m d 3 i k B T / 2 0 ( d as particles diameter) [6].
2
Thus, effective susceptibility of ZnFe2O4, i is 1.49 10 , coupling constant between particles,
0 m 2 / 2d 3 k BT , is calculated as 3.73 102 . α-FeOOH nanoparticles is weak magnetic,
3
3
effective susceptibility, i , is 9.80 10 , coupling constant between particles, , is 2.45 10 .
3.2. Field-Deduced Effect of Light Transmission for Sample ZnFe2O4 Ferrofluids
At the experiment, sample ZnFe2O4 ferrofluids is placed in the experiment device. It’s
30s after transmitted light becomes stable, respectively, that 700Gs, 900Gs, 1100Gs and
1300Gs of magnetic field is coupled. It’s observed that the intensity of transmitted light
unchanged over time. Even when the magnetic field is removed from the 1200s, its light
transmittance remains the same over time. As shown in Figure 3.
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(a) the ZnFe2O4 particles
(b)
(b) the α-FeOOH particles
Figure 2. Magnetization curve and TEM picture of the particles
Figure 3. Field-deduced effect of light transmission for sample ZnFe2O4 ferrofluids when the
magnetic field is 1300Gs
The Field-Induced Effect of Light Transmission for FeOOH-ZnFe2O4 … (Anrong Wang)
309
ISSN: 1693-6930
3.3. Field-Deduced Effect of Light Transmission for Sample FeOOH Ferrofluids
Sample FeOOH Ferrofluids is placed in the experiment device. It’s 30s after transmitted
light becomes stable, respectively, 700Gs, 900Gs, 1100Gs and 1300Gs of magnetic field is
coupled. The intensity of transmitted light is observed over time. Even when the magnetic field
is removed from the 1200s, its light transmittance remains the same over time, as shown in
Figure 4.
(a) when the magnetic field is 700Gs
(b) when the magnetic field is 900Gs
(c) when the magnetic field is 1100Gs
(d) when the magnetic field is 1300Gs
Figure 4. Field-deduced effect of light transmission for sample FeOOH ferrofluid
From the experiment, the moment the magnetic field is coupled to the sample FeOOH
ferrofluids, the rates of light transmission increases greatly before it remain stable. When the
magnetic field is removed, the light transmission returns to 1 quickly.
3.4. Field-Deduced Effect of Light Transmission for Sample FeOOH-ZnFe2O4 Ferrofluids
Sample FeOOH-ZnFe2O4 ferrofluids is placed in the experiment device. It’s 30s after
transmitted light becomes stable, respectively, 700Gs, 900Gs, 1100Gs and 1300Gs of magnetic
field is coupled. The magnetic field is removed after the 1200s. The intensity of transmitted light
is observed over time, as shown in Figure 5.
From the experiment, the moment the magnetic field is coupled to the sample
ferrofluids, the rates of light transmission increases greatly. The stronger the field, the more
intensified the light transmission. When the magnetic field is removed, the light transmission
drops and returns to 1 or so.
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ISSN: 1693-6930
(a) when the magnetic field is 700Gs
(b) when the magnetic field is 900Gs
(c) when the magnetic field is 1100Gs
(d) when the magnetic field is 1300Gs
310
Figure 5. Field-deduced effect of light transmission for sample FeOOH-ZnFe2O4 Ferrofluids
4. Discussions
4.1. Analysis of Field-Deduced Effect of Light Transmission for Sample ZnFe2O4
Ferrofluid
From Figure 3, it can be deduced that nanoparticles in ZnFe2O4 ferrofluid don’t form
aggregate, under the effect of static magnetic, applied external magnetic field. That is because
inherent magnetic moment of ZnFe2O4 ferrofluid, is smaller than 1[7, 8], which tends to the
magnetic field but can’t form aggregate or change the intensity of light transmission. External
magnetic field removed, ZnFe2O4 ferrofluid restores to the original state in Brownian motion and
Neil rotating.
4.2. Analysis of Field-Deduced Effect of Light Transmission for Sample FeOOH
Ferrofluids
From Figure 4, the moment the magnetic field is applied to the sample FeOOH
ferrofluids, the rates of light transmission increases greatly. When the magnetic field is removed,
the light transmission returns to 1 quickly. Inherent magnetic moment of α-FeOOH ferrofluid,
is smaller than 1, applied external magnetic field, magnetic interaction between nanoparticles in
ZnFe2O4 ferrofluid can’t form aggregate so as to cause magneto-optical effect. It can be
deduced that the field-deduced effect of light transmission for sample FeOOH Ferrofluids is
caused by α-FeOOH nanoparticles’ optical anisotropy. α-FeOOH nanoparticles are in magnetic
dielectric ellipsoid system of the cubic crystal system. External magnetic field applied, ellipsoid
orientation order changes optical characteristic from the isotropic to anisotropic, which leads to
the field-deduced light transmission [9,10]. When the magnetic field is removed, the light
The Field-Induced Effect of Light Transmission for FeOOH-ZnFe2O4 … (Anrong Wang)
311
ISSN: 1693-6930
transmission returns to 1 quickly. It proves order of dielectric ellipsoid is caused by rotation of
the ellipsoid’s intrinsic magnetic moment under external magnetic field. External magnetic field
removed, dielectric ellipsoid with intrinsic magnetic moment restores to the balance in Brownian
motion and Neil rotating.
4.3. Analysis of Field-Deduced Effect of Light Transmission for Sample FeOOH-ZnFe2O4
Ferrofluids
From Figure 5, when the magnetic field is applied, the field-deduced effect of light
transmission for sample FeOOH-ZnFe2O4 ferrofluids is similar to that of the sample FeOOH
Ferrofluids, which is not the simple overlapping of two effects. The field-deduced effect of light
transmission for sample FeOOH-ZnFe2O4 ferrofluids is more obvious than that of the sample
FeOOH ferrofluids. α-FeOOH nanoparticles and ZnFe2O4 nanoparticles are weak magnetic,
coupling constant of α-FeOOH nanoparticles and ZnFe2O4 nanoparticles is calculated as
3.09 10 3 . Magnetic interaction between nanoparticles in α-FeOOH and ZnFe2O4 can’t form
aggregate so as to cause magneto-optical effect. The similarity of the effects proves the fielddeduced effect of light transmission for sample FeOOH-ZnFe2O4 Ferrofluids is caused by αFeOOH nanoparticles’ optical anisotropy. Ellipsoid orientation order changes optical
characteristic from the isotropic to anisotropic, which leads to the field-deduced light
transmission. External magnetic field is applied, the nanoparticles is ferromagnetic or ferrous
single domain nanoparticles of 10nmor so. Its interaction potential with the magnetic can be
described as:
U m H m H
(2)
Of which is the permeability. From the equation, under the influence the magnetic
field, magnetic moment of the particles tends to the field direction. If α-FeOOH nanoparticles
were rigid particles, the rotation of the magnetic moment would bring the rotation of the whole
particles. As α-FeOOH is orthogonal crystal structure, whose dielectric constant is anisotropy,
the rotation of the magnetic moment causes the change of dielectric constant, which leads to
the change of the intensity of the light transmission. The rate of permeability can be referred as:
0r
(3)
Of which ߤ is the permeability of vacuum, ߤ is the relative permeability of medium. In
vacuum or nonmagnetic medium, ߤ is 1[11, 12]. ZnFe2O4 particle of FeOOH-ZnFe2O4 binary
ferrofluids can be regarded as the background of FeOOH nanoparticles [1], which decreases
the effective relative permeability. The particles are more likely to tend to the field direction,
which makes the field-deduced dielectric properties change more obvious, and change of the
light transmission intensity more impressive.
5. Conclusions
Experiment of field-deduced effect of light transmission for sample ZnFe2O4 ferrofluids
shows nanoparticles is weak magnetic. Nanoparticles can’t form aggregate, they tend to be
magnetic field directed. Nanoparticles are of the cubic lattice system and isotropic, wouldn’t
cause the change of intensity of light. External magnetic field removed, ZnFe2O4 ferrofluids
restores to the original state in Brownian motion and Neil rotating [13, 14].
Experiment of field-deduced effect of light transmission for sample FeOOH ferrofluid
shows nanoparticles is weak magnetic. When external magnetic field is applied, magnetic
interaction between nanoparticles can’t form aggregate. α-FeOOH nanoparticles are in
magnetic dielectric ellipsoid system of the cubic crystal system. External magnetic field applied,
ellipsoid orientation order changes optical characteristic from the isotropic to anisotropic, which
leads to the field-deduced light transmission. External magnetic field removed, FeOOH dielectric
ellipsoid restores to the balance in Brownian motion and Neil rotating.
Experiment of field-deduced effect of light transmission for sample FeOOH ferrofluid
shows the field-deduced effect of light transmission for sample FeOOH-ZnFe2O4 ferrofluids is
not the simple overlapping of that of FeOOH and FeOOH-ZnFe2O4 ferrofluids. The fieldTELKOMNIKA Vol. 14, No. 3A, September 2016 : 306 – 312
TELKOMNIKA
ISSN: 1693-6930
312
deduced effect of light transmission for sample FeOOH-ZnFe2O4 ferrofluids is caused by αFeOOH nanoparticles’ optical anisotropy. Ellipsoid orientation order changes optical
characteristic from the isotropic to anisotropic, which leads to the field-deduced microstructure
change and improve the macro field-deduced light transmission of FeOOH ferrofluid. So
FeOOH-ZnFe2O4 binary ferrofluids has a better magnetic response than FeOOH ferrofluids.
Acknowledgements
Financial support for this work was provided by the National Natural Science
Foundation of China (No.61107064), the Chongqing University Innovation Team Founding,
China (No.KJTD201320), the Frontier and Applied Basic Research Project of Chongqing,
China (No.cstc2014jcyjA1302 and No.cstc2016jcyjA1233), the Science Technology Special
Funds in Wanzhou District, and the Chongqing Graduate Scientific Research Innovation Project
(No.CYS15225).
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The Field-Induced Effect of Light Transmission for FeOOH-ZnFe2O4 … (Anrong Wang)
ISSN: 1693-6930, accredited A by DIKTI, Decree No: 58/DIKTI/Kep/2013
DOI: 10.12928/TELKOMNIKA.v14i3A.4438
306
The Field-Induced Effect of Light Transmission for
FeOOH-ZnFe2O4 Ferrofluids Control
Anrong Wang*1, Pengzhi Wei2, Yufeng Shao3, Xiangfei Nie4, Kezhong Liang5, Haiyan
Huang6
1,3,4,5,6
Key Laboratory of Signal and Information Processing, Chongqing Three Gorges University,
Wanzhou District, Chongqing, 404100, P. R. China
2
College of Science, Harbin Engineering University, Nangang District, Harbin, 150006, P. R. China
*Corresponding author, e-mail: [email protected]
Abstract
The paper is supposed to find the change of the light transmission rate with the change of time of
the same volume fraction of ZnFe2O4 ferrofluids, FeOOH ferrofluids and FeOOH-ZnFe2O4 binary
ferrofluids, applied in different magnetic field, in parallel to the light direction. The field-induced effects of
light transmission for the three ferrofluids are compared, so as to explore the reason from the
microstructure change of the ferrofluids.
Keywords: Ferrofluids, magnetic field, light transmission, field-induced effect
Copyright © 2016 Universitas Ahmad Dahlan. All rights reserved.
1. Introduction
Ferrofluids refer to the colloidal suspensions dispersed of the strong magnetic
nanoparticles in certain carried liquid. Applied in the magnetic field, magnetic particles form a
chain, orderly arrange along the direction of the magnetic field, creating optical anisotropy.
Researches have been carried out on light transmission change and resilience of magnetic
nanoparticles under the effect of the magnetic field [1-3]. Based on that [4], the paper is to make
a comparison of the field-induced effect of light transmission for weak magnetic ZnFe2O4
ferrofluids, FeOOH ferrofluids and FeOOH-ZnFe2O4 binary ferrofluids, as well as to present the
rule and mechanism of the field-deduced light transmission.
2. Materials and Methods
2.1. The Preparation of Samples
The ZnFe2O4 and α-FeOOH nanoparticles are produced by chemical co-precipitation
technology with FeCl3, ZnCl2, NaOH, HCl, and HNO3. Then Q = 0.04, v=0.4% FeOOH of ionic
ferrofluid and Q = 0.04, v=0.4% ionic ferrofluid are synthesized, in the end, FeOOH mixed with
magnetic liquid ZnFe2O4 as FeOOH-ZnFe2O4 dual magnetic liquid. The FeOOH-ZnFe2O4 binary
ferrofluids are obtained by mixing both the ferrofluids.
The samples are ZnFe2O4 ferrofluids, FeOOH ferrofluids and FeOOH-ZnFe2O4 binary
ferrofluids, in the flat glass case, made into (15mm×15mm×0.53mm) film-like light transmission
samples.
2.2. Experimental Apparatus Figure of Field-Deduced Light Transmission
As shown in Figure 1, a laser beam L produced by He-Ne laser irradiate spectroscope
b, divided into two beams of light L1 and L2. Beams L1 go through the magnetic field (sample)
with e1 magnetic liquids in, then pass the adjustable polarizer c1, and expose to the silicon
photocell f1. Beam L2 directly go through the magnetic liquid e2 (sample for reference), then
pass the adjustable polarizer C2, and expose to the silicon photocell f2. Silicon photocell f1 and f2
convert the light signal strength of L1 and L2, respectively, for the current intensity, which are
input and analyzed by the computer, to get the intensity of laser beams L1 and L2. The values of
intensity of the I1, I2, are marked by silicon photocell electrical signal (mV for intensity value). To
Received March 27, 2016; Revised July 22, 2016; Accepted August 3, 2016
307
ISSN: 1693-6930
measure light transmission, one need to adjust adjustable polarizer light L1 and L2 until equal
light intensity values is reached. The beam intensity ratio η＝I1/I2 is defined as light
transmittance, namely relative transmittance of light. Without magnetic field, the relative light
transmittance is 1, with magnetic field, the relative light transmittance can tell the influence of
field-deduced light transmission for the ferrofluids. At room temperature, the effect of fielddeduced light transmission for samples ZnFe2O4 ferrofluids, FeOOH ferrofluids and FeOOHZnFe2O4 binary ferrofluids are measured, the corresponding mechanism are analyzed
theoretically.
Figure 1. The sketch map of experimental device
3. Results
3.1. The TEM and VSM Measure of ZnFe2O4 and α-FeOOH Nanoparticles
Figure Figure 2(a) and Figure 2(b) are the TEM and VSM test chart of ZnFe2O4 and αFeOOH nanoparticles. From the figure both are ball-shaped. Size distribution of the
nanoparticles, produced by chemical co-precipitation technology, is lognormal distributed.
d
d ln x
g
(ln x ln x g )
1
exp[
]
2 ln 2 g
2 ln g
2
(1)
x
Where x the diameter of the nanoparticles, g is the geometric average particle size,
is the geometric standard deviation of size distribution. So 4.22nm and 8.16nm are the
geometric average particle sizes of ZnFe2O4 nanoparticles and α-FeOOH nanoparticles, 0.26 is
the geometric deviations.
As ZnFe2O4 is weak magnetic, its magnetization curve is linear, the initial susceptibility
1/ 2
i (dM / dH ) H 0 0 mM s / 3k BT [5], of which m d 3 i k B T / 2 0 ( d as particles diameter) [6].
2
Thus, effective susceptibility of ZnFe2O4, i is 1.49 10 , coupling constant between particles,
0 m 2 / 2d 3 k BT , is calculated as 3.73 102 . α-FeOOH nanoparticles is weak magnetic,
3
3
effective susceptibility, i , is 9.80 10 , coupling constant between particles, , is 2.45 10 .
3.2. Field-Deduced Effect of Light Transmission for Sample ZnFe2O4 Ferrofluids
At the experiment, sample ZnFe2O4 ferrofluids is placed in the experiment device. It’s
30s after transmitted light becomes stable, respectively, that 700Gs, 900Gs, 1100Gs and
1300Gs of magnetic field is coupled. It’s observed that the intensity of transmitted light
unchanged over time. Even when the magnetic field is removed from the 1200s, its light
transmittance remains the same over time. As shown in Figure 3.
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(a) the ZnFe2O4 particles
(b)
(b) the α-FeOOH particles
Figure 2. Magnetization curve and TEM picture of the particles
Figure 3. Field-deduced effect of light transmission for sample ZnFe2O4 ferrofluids when the
magnetic field is 1300Gs
The Field-Induced Effect of Light Transmission for FeOOH-ZnFe2O4 … (Anrong Wang)
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3.3. Field-Deduced Effect of Light Transmission for Sample FeOOH Ferrofluids
Sample FeOOH Ferrofluids is placed in the experiment device. It’s 30s after transmitted
light becomes stable, respectively, 700Gs, 900Gs, 1100Gs and 1300Gs of magnetic field is
coupled. The intensity of transmitted light is observed over time. Even when the magnetic field
is removed from the 1200s, its light transmittance remains the same over time, as shown in
Figure 4.
(a) when the magnetic field is 700Gs
(b) when the magnetic field is 900Gs
(c) when the magnetic field is 1100Gs
(d) when the magnetic field is 1300Gs
Figure 4. Field-deduced effect of light transmission for sample FeOOH ferrofluid
From the experiment, the moment the magnetic field is coupled to the sample FeOOH
ferrofluids, the rates of light transmission increases greatly before it remain stable. When the
magnetic field is removed, the light transmission returns to 1 quickly.
3.4. Field-Deduced Effect of Light Transmission for Sample FeOOH-ZnFe2O4 Ferrofluids
Sample FeOOH-ZnFe2O4 ferrofluids is placed in the experiment device. It’s 30s after
transmitted light becomes stable, respectively, 700Gs, 900Gs, 1100Gs and 1300Gs of magnetic
field is coupled. The magnetic field is removed after the 1200s. The intensity of transmitted light
is observed over time, as shown in Figure 5.
From the experiment, the moment the magnetic field is coupled to the sample
ferrofluids, the rates of light transmission increases greatly. The stronger the field, the more
intensified the light transmission. When the magnetic field is removed, the light transmission
drops and returns to 1 or so.
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ISSN: 1693-6930
(a) when the magnetic field is 700Gs
(b) when the magnetic field is 900Gs
(c) when the magnetic field is 1100Gs
(d) when the magnetic field is 1300Gs
310
Figure 5. Field-deduced effect of light transmission for sample FeOOH-ZnFe2O4 Ferrofluids
4. Discussions
4.1. Analysis of Field-Deduced Effect of Light Transmission for Sample ZnFe2O4
Ferrofluid
From Figure 3, it can be deduced that nanoparticles in ZnFe2O4 ferrofluid don’t form
aggregate, under the effect of static magnetic, applied external magnetic field. That is because
inherent magnetic moment of ZnFe2O4 ferrofluid, is smaller than 1[7, 8], which tends to the
magnetic field but can’t form aggregate or change the intensity of light transmission. External
magnetic field removed, ZnFe2O4 ferrofluid restores to the original state in Brownian motion and
Neil rotating.
4.2. Analysis of Field-Deduced Effect of Light Transmission for Sample FeOOH
Ferrofluids
From Figure 4, the moment the magnetic field is applied to the sample FeOOH
ferrofluids, the rates of light transmission increases greatly. When the magnetic field is removed,
the light transmission returns to 1 quickly. Inherent magnetic moment of α-FeOOH ferrofluid,
is smaller than 1, applied external magnetic field, magnetic interaction between nanoparticles in
ZnFe2O4 ferrofluid can’t form aggregate so as to cause magneto-optical effect. It can be
deduced that the field-deduced effect of light transmission for sample FeOOH Ferrofluids is
caused by α-FeOOH nanoparticles’ optical anisotropy. α-FeOOH nanoparticles are in magnetic
dielectric ellipsoid system of the cubic crystal system. External magnetic field applied, ellipsoid
orientation order changes optical characteristic from the isotropic to anisotropic, which leads to
the field-deduced light transmission [9,10]. When the magnetic field is removed, the light
The Field-Induced Effect of Light Transmission for FeOOH-ZnFe2O4 … (Anrong Wang)
311
ISSN: 1693-6930
transmission returns to 1 quickly. It proves order of dielectric ellipsoid is caused by rotation of
the ellipsoid’s intrinsic magnetic moment under external magnetic field. External magnetic field
removed, dielectric ellipsoid with intrinsic magnetic moment restores to the balance in Brownian
motion and Neil rotating.
4.3. Analysis of Field-Deduced Effect of Light Transmission for Sample FeOOH-ZnFe2O4
Ferrofluids
From Figure 5, when the magnetic field is applied, the field-deduced effect of light
transmission for sample FeOOH-ZnFe2O4 ferrofluids is similar to that of the sample FeOOH
Ferrofluids, which is not the simple overlapping of two effects. The field-deduced effect of light
transmission for sample FeOOH-ZnFe2O4 ferrofluids is more obvious than that of the sample
FeOOH ferrofluids. α-FeOOH nanoparticles and ZnFe2O4 nanoparticles are weak magnetic,
coupling constant of α-FeOOH nanoparticles and ZnFe2O4 nanoparticles is calculated as
3.09 10 3 . Magnetic interaction between nanoparticles in α-FeOOH and ZnFe2O4 can’t form
aggregate so as to cause magneto-optical effect. The similarity of the effects proves the fielddeduced effect of light transmission for sample FeOOH-ZnFe2O4 Ferrofluids is caused by αFeOOH nanoparticles’ optical anisotropy. Ellipsoid orientation order changes optical
characteristic from the isotropic to anisotropic, which leads to the field-deduced light
transmission. External magnetic field is applied, the nanoparticles is ferromagnetic or ferrous
single domain nanoparticles of 10nmor so. Its interaction potential with the magnetic can be
described as:
U m H m H
(2)
Of which is the permeability. From the equation, under the influence the magnetic
field, magnetic moment of the particles tends to the field direction. If α-FeOOH nanoparticles
were rigid particles, the rotation of the magnetic moment would bring the rotation of the whole
particles. As α-FeOOH is orthogonal crystal structure, whose dielectric constant is anisotropy,
the rotation of the magnetic moment causes the change of dielectric constant, which leads to
the change of the intensity of the light transmission. The rate of permeability can be referred as:
0r
(3)
Of which ߤ is the permeability of vacuum, ߤ is the relative permeability of medium. In
vacuum or nonmagnetic medium, ߤ is 1[11, 12]. ZnFe2O4 particle of FeOOH-ZnFe2O4 binary
ferrofluids can be regarded as the background of FeOOH nanoparticles [1], which decreases
the effective relative permeability. The particles are more likely to tend to the field direction,
which makes the field-deduced dielectric properties change more obvious, and change of the
light transmission intensity more impressive.
5. Conclusions
Experiment of field-deduced effect of light transmission for sample ZnFe2O4 ferrofluids
shows nanoparticles is weak magnetic. Nanoparticles can’t form aggregate, they tend to be
magnetic field directed. Nanoparticles are of the cubic lattice system and isotropic, wouldn’t
cause the change of intensity of light. External magnetic field removed, ZnFe2O4 ferrofluids
restores to the original state in Brownian motion and Neil rotating [13, 14].
Experiment of field-deduced effect of light transmission for sample FeOOH ferrofluid
shows nanoparticles is weak magnetic. When external magnetic field is applied, magnetic
interaction between nanoparticles can’t form aggregate. α-FeOOH nanoparticles are in
magnetic dielectric ellipsoid system of the cubic crystal system. External magnetic field applied,
ellipsoid orientation order changes optical characteristic from the isotropic to anisotropic, which
leads to the field-deduced light transmission. External magnetic field removed, FeOOH dielectric
ellipsoid restores to the balance in Brownian motion and Neil rotating.
Experiment of field-deduced effect of light transmission for sample FeOOH ferrofluid
shows the field-deduced effect of light transmission for sample FeOOH-ZnFe2O4 ferrofluids is
not the simple overlapping of that of FeOOH and FeOOH-ZnFe2O4 ferrofluids. The fieldTELKOMNIKA Vol. 14, No. 3A, September 2016 : 306 – 312
TELKOMNIKA
ISSN: 1693-6930
312
deduced effect of light transmission for sample FeOOH-ZnFe2O4 ferrofluids is caused by αFeOOH nanoparticles’ optical anisotropy. Ellipsoid orientation order changes optical
characteristic from the isotropic to anisotropic, which leads to the field-deduced microstructure
change and improve the macro field-deduced light transmission of FeOOH ferrofluid. So
FeOOH-ZnFe2O4 binary ferrofluids has a better magnetic response than FeOOH ferrofluids.
Acknowledgements
Financial support for this work was provided by the National Natural Science
Foundation of China (No.61107064), the Chongqing University Innovation Team Founding,
China (No.KJTD201320), the Frontier and Applied Basic Research Project of Chongqing,
China (No.cstc2014jcyjA1302 and No.cstc2016jcyjA1233), the Science Technology Special
Funds in Wanzhou District, and the Chongqing Graduate Scientific Research Innovation Project
(No.CYS15225).
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The Field-Induced Effect of Light Transmission for FeOOH-ZnFe2O4 … (Anrong Wang)