VNU Journal of Science, Mathematics - Physics 25 (2009) 153-159
153
The effect of cobalt substitution on structure
and magnetic properties of nickel ferrite
Nguyen Khanh Dung
1,
*, Nguyen Hoang Tuan
2
1
Industry University, Ho Chi Minh City,
12 Nguyen Van Bao, Ward 4, Go Vap District, Hochiminh city, Vietnam
2
Can Tho University, 3-2 Street, Can Tho city, Vietnam
Received 15 August 2009
Abstract. A series of cobalt doped nickel ferrite with composition of Ni
1-X
Co
X
Fe
2
O
4
with x ranges
from 0.0 to 0.8 (in steps of 0.2) was prepared by using co-precipitation method and subsequently
sintered, annealed at 600
0
C for 3h. The influence of the Co content on the crystal lattice parameter,
the stretching vibration and the magnetization of specimens were subsequently studied. XRD and
FTIR were used to investigate structure and composition variations of the samples. All samples
were found to have a cubic spinel structure. TEM was used to study morphological variations. The
results indicate that the average particle sizes are between 29÷35 nm. B-H hysteresis measurement
was carried out at room temperature under field of 5 kOe and this measurement with the increase
of Co
2+
concentration yields the monotonic increase of saturation magnetization (M
S
) and coercive
field (H
C
). Ferrites with such behavior are important for magnetic recording media, microwave
applications, environment and medical biology [1-3]. In view of this, we have studied the various
properties of Co doped Ni ferrite.
1. Introduction
NiFe
2
O
4
has cubic inverse spinel structure with Ni
2+
ions occupy octahedral B – site and Fe
3+
ions
occupy both tetrahedral A – sites and octahedral B – sites [4]. Nickel ferrite has been prepared by
standard ceramic route. That are particle size micrometer, low saturation magnetization and low
coercivity. To our knowledge, the systematic investigation of the magnetic and electrical properties of
Ni
1-X
Co
X
Fe
2
O
4
with x varied from 0 to 0.8 in steps of 0.2 has not been reported so far. Further Ni-Co
ferrite shows the good magnetostrictive properties among all the ferrite family. The studies on doping
of good magnetostrictive material into the highly resistive nickel ferrite is one of the important phase
for consideration of challenging magnetoelectric materials. Therefore by keeping this view in our
mind we have proposed the studies on structural analysis and magnetic properties of Co–Ni ferrite
with the above mentioned compositions by co – precipitation method, a new method for preparation of
ferrite [5-6].
The results shown prepared Ni
1-X
Co
X
Fe
2
O
4
powder ferrite had the particle sizes in nanometers and
good magnetic properties:
- Saturation Magnetization M
S
about 47-67 emu/g,
______
*
Corresponding author. E-mail: nkdung@yahoo.com
N.K. Dung, N.H. Tuan / VNU Journal of Science, Mathematics - Physics 25 (2009) 153-159
154
- Coercivity H
C
from 31 Oe (with x=0.0) to 871 Oe (with x=0.8),
- Average longitudinal Magnetostriction λ
//
= (80-120).10
-6
- Magnetomechanic Quality Q=3100 (with x=0.0)
2. Experimental
2.1. Synthesis of Ni-Co powder ferrite
A series of cobalt doped nickel ferrite with composition of Ni
1-X
Co
X
Fe
2
O
4
with x ranges from 0.0
to 0.8 (in steps of 0.2) was prepared by co-precipitation method. For Eddy Currents and Magnetic Damping Eddy Currents and Magnetic Damping Bởi: OpenStaxCollege Eddy Currents and Magnetic Damping As discussed in Motional Emf, motional emf is induced when a conductor moves in a magnetic field or when a magnetic field moves relative to a conductor If motional emf can cause a current loop in the conductor, we refer to that current as an eddy current Eddy currents can produce significant drag, called magnetic damping, on the motion involved Consider the apparatus shown in [link], which swings a pendulum bob between the poles of a strong magnet (This is another favorite physics lab activity.) If the bob is metal, there is significant drag on the bob as it enters and leaves the field, quickly damping the motion If, however, the bob is a slotted metal plate, as shown in [link](b), there is a much smaller effect due to the magnet There is no discernible effect on a bob made of an insulator Why is there drag in both directions, and are there any uses for magnetic drag? A common physics demonstration device for exploring eddy currents and magnetic damping (a) The motion of a metal pendulum bob swinging between the poles of a magnet is quickly damped by the action of eddy currents (b) There is little effect on the motion of a slotted metal bob, implying that eddy currents are made less effective (c) There is also no magnetic damping on a nonconducting bob, since the eddy currents are extremely small [link] shows what happens to the metal plate as it enters and leaves the magnetic field In both cases, it experiences a force opposing its motion As it enters from the left, 1/6 Eddy Currents and Magnetic Damping flux increases, and so an eddy current is set up (Faraday’s law) in the counterclockwise direction (Lenz’s law), as shown Only the right-hand side of the current loop is in the field, so that there is an unopposed force on it to the left (RHR-1) When the metal plate is completely inside the field, there is no eddy current if the field is uniform, since the flux remains constant in this region But when the plate leaves the field on the right, flux decreases, causing an eddy current in the clockwise direction that, again, experiences a force to the left, further slowing the motion A similar analysis of what happens when the plate swings from the right toward the left shows that its motion is also damped when entering and leaving the field A more detailed look at the conducting plate passing between the poles of a magnet As it enters and leaves the field, the change in flux produces an eddy current Magnetic force on the current loop opposes the motion There is no current and no magnetic drag when the plate is completely inside the uniform field When a slotted metal plate enters the field, as shown in [link], an emf is induced by the change in flux, but it is less effective because the slots limit the size of the current loops Moreover, adjacent loops have currents in opposite directions, and their effects cancel When an insulating material is used, the eddy current is extremely small, and so magnetic damping on insulators is negligible If eddy currents are to be avoided in conductors, then they can be slotted or constructed of thin layers of conducting material separated by insulating sheets 2/6 Eddy Currents and Magnetic Damping Eddy currents induced in a slotted metal plate entering a magnetic field form small loops, and the forces on them tend to cancel, thereby making magnetic drag almost zero Applications of Magnetic Damping One use of magnetic damping is found in sensitive laboratory balances To have maximum sensitivity and accuracy, the balance must be as friction-free as possible But if it is friction-free, then it will oscillate for a very long time Magnetic damping is a simple and ideal solution With magnetic damping, drag is proportional to speed and becomes zero at zero velocity Thus the oscillations are quickly damped, after which the damping force disappears, allowing the balance to be very sensitive (See [link].) In most balances, magnetic damping is accomplished with a conducting disc that rotates in a fixed field 3/6 Eddy Currents and Magnetic Damping Magnetic damping of this sensitive balance slows its oscillations Since Faraday’s law of induction gives the greatest effect for the most rapid change, damping is greatest for large oscillations and goes to zero as the motion stops Since eddy currents and magnetic damping occur only in conductors, recycling centers can use magnets to separate metals from other materials Trash is dumped in batches down a ramp, beneath which lies a powerful magnet Conductors in the trash are slowed by magnetic damping while nonmetals in the trash move on, separating from the metals (See [link].) This works for all metals, not just ferromagnetic ones A magnet can separate out the ferromagnetic materials alone by acting on stationary trash Metals can be separated from other trash by magnetic drag Eddy currents and magnetic drag are created in ...[...]... 2.1 SPIN AND ORBITAL STATES OF ELECTRONS In the following, it is assumed that the reader has some elementary knowledge of quantum mechanics In this section, the vector model of magnetic atoms will be briefly reviewed which may serve as reference for the more detailed description of the magnetic behavior of localized moment systems described further on Our main interest in the vector model of magnetic. .. limited 4.2 FERROMAGNETISM The total field experienced by the magnetic moments comprises the applied field H and the molecular field or Weiss field We will first investigate the effect of the presence of the Weiss field on the magnetic behavior of a ferromagnetic material above In this case, the magnetic moments are no longer ferromagnetically ordered and the system is paramagnetic Therefore, we may... here on those fundamental aspects of magnetism of the solid state that form the basis for the various applications mentioned and from which the most salient of their properties can be understood It will be clear that all these matters cannot be properly treated without a discussion of some basic features of magnetism In the first part a brief survey will therefore be given of the origin of magnetic moments,... structures have also been included in Table 4.1.1 The shortest Fe–Fe distances, for which antiferromagnetic couplings are predicted to occur according to Fig 4.1.1, are seen to adopt a wide gamut of values on either side of the Fe–Fe distance in Fe metal 22 CHAPTER 4 THE MAGNETICALLY ORDERED STATE This does not lend credence to the notion that short Fe–Fe distances favor antiferromagnetic interactions Equally... external flux density of in an external field more details about units will be discussed 14 CHAPTER 3 PARAMAGNETISM OF FREE IONS in Chapter 8) For one has J = 9/2 and g = 8/11 (see Table 2.2.1) Furthermore, we make use of the following values and At room temperature (298 K) , one derives for y in Eq (3.1.11): Since we now have shown that under the above conditions, it is justified to use only the first... direction of the field For practical reason, we will drop the subscript J and write simply m to indicate the magnetic quantum number associated with the total angular momentum This page intentionally left blank 3 Paramagnetism of Free Ions 3.1 THE BRILLOUIN FUNCTION Once we have applied the vector model and Hund’s rules to find the quantum numbers J, L, and S of the ground-state multiplet of a given type of. .. value of the Physica B 392 (2007) 154–158
Synthesis, structure and magnetic properties of
iron-doped tungsten oxide nanorods
P.Z. Si
a,b,c,Ã
, C.J. Choi
b
, E. Bru
¨
ck
c
, J.C.P. Klaasse
c
, D.Y. Geng
a
, Z.D. Zhang
a
a
Shenyang National Laboratory for Materials Science and International Centre for Materials Physics, Institute of Metal Research,
Chinese Academy of Sciences, Shenyang 110016, China
b
Korea Institute of Machinery and Materials, 66 Sangnam-dong, Changwon 641-010, South Korea
c
Van der Waals Zeeman Institute, University of Amsterdam, Valckenierstr 65, NL-1018 XE Amsterdam, The Netherlands
Received 19 June 2006; received in revised form 6 November 2006; accepted 9 November 2006
Abstract
Iron-doped tungsten oxide nanorods of 20–30 nm in diameter and 60–2000 nm in length have been prepared by an arc discharge route
using W as cathode and a mixture of Fe and NiO as anode, in which NiO serves as oxygen source. The characteristics of the nanorods
were investigated systematically by using X-ray diffraction, transmission electron microscopy, energy dispersive spectra, X-ray
photoelectron spectroscopy, and superconducting quantum interference device magnetometer. The nanorods were mainly composed of
tungsten, iron and their oxides. The iron-rich phase in the nanorods exhibits soft ferromagnetic behaviors with zero coercivity and zero
remanence and a decreased Curie temperature of 1000 K. Heat-treatment of the sample in air induces oxidation of elemental Fe, resulting
in the reduction of the magnetization.
r 2006 Elsevier B.V. All rights reserved.
PACS: 75.75.þa; 81.07.Wx
Keywords: Iron; Nanorods; Magnetic properties; Tungsten oxide
1. Introduction
Nanomaterials have been the subject of intense research
in recent years because of their unique properties in
comparison with the bulk counterparts an d their existing
and/or potential applications in a wide variety of areas
such as information storage, electronics, sensors, structural
components, catalysis, etc. Two-dimensional WO
3
films
have been widely studied for their use in gas sensors [1].
One-dimensional WO
3
nanorods, which can be prepared
by using a few different approaches, as partially described
below, are attracting increasingly attention recently.
Nanorods of the mixtures of WO
2
and WO
3
were obtaine d
via amorphous tungsten oxide nanoparticles [2]. Electro-
chemical etching followed by heating yielded WO
3
nanorods on W substrates [3]. Through the controlled
removal of surfactant from the pre-synthesized mesola-
mellar at elevated temperature, WO
3
nanowires were
obtained [4].WO
3
nanorods have also been generated by
heating the tungsten filament using SiO
2
[5],B
2
O
3
[6], air
[7], and H
2
O as oxygen sources [8]. In this work, we report
on the formation of Fe-doped tungsten oxide nanorods by
arc discharge method, using NiO as oxygen sources.
The magnetic behaviors of atomic and bulk transition
metals are i ntrinsically d ifferent. Consequently, t he magnetic
properties of nanoparticles as a bridge in the atomic and bulk
materials are very sensitive to size, composition, and local
atomic environment, thus showing a wide variety of intriguing
phenomena [9] . In this work, the magnetic properties o f t he
WO
3
/Fe nanorods were investigated systematically.
2. Experimenta l
The WO
3
/Fe nanorods were prepared by using the
traditional arc discharge method, which had been widely
ARTICLE IN PRESS
www.elsevier.com/locate/physb
0921-4526/$ - see front matter r 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.physb.2006.11.011
Ã
Corresponding author. Department of 1
H NMR study of the molecular structure and magnetic properties
of the active site for the cyanomet complex of O
2
-avid hemoglobin
from the trematode
Paramphistomum epiclitum
Weihong Du
1
, Zhicheng Xia
1
, Sylvia Dewilde
2
, Luc Moens
2
and Gerd N. La Mar
1
1
Department of Chemistry, University of California, Davis, CA, USA;
2
Department of Biomedical Sciences,
University of Antwerp, Wilrijk, Belgium
The solution molecular and electronic structures of the active
site in the extremely O
2
-avid hemoglobin from the trematode
Paramphistomum epiclitum have been investigated by
1
H
NMR on the cyanomet form in order to elucidate the distal
hydrogen-bonding to a ligated H-bond acceptor ligand.
Comparison of the strengths of dipolar interactions in
solution with the alternate crystal structures of methemo-
globin establish that the solution structure of wild-type Hb
more closely resembles the crystal structure of the recom-
binant wild-type than the true wild-type met-hemoglobin.
The distal Tyr66(E7) is found oriented out of the heme
pocket in solution as found in both crystal structures. Ana-
lysis of dipolar contacts, dipolar shift and paramagnetic
relaxation establishes that the Tyr32(B10) hydrogen proton
adopts an orientation that allows it to make a strong H-bond
to the bound cyanide. The observation of a significant iso-
tope effect on the heme methyl contact shifts confirms a
strong contact between the Tyr32(B10) OH and the ligated
cyanide. The quantitative determination of the orientation
and anisotropies of the paramagnetic susceptibility tensor
reveal that the cyanide is tilted %10° from the heme normal
so as to avoid van der Waals overlap with the Tyr32(B10)
Og. The pattern of heme contact shifts with large low-field
shifts for 7-CH
3
and 18-CH
3
is shown to arise not from the
180° rotation about the a-c-meso axis, but due to the %45°
rotation of the axial His imidazole ring, relative to that in
mammalian globins.
Keywords: hemoglobin; trematode; H-bonding; dipolar
shift; NMR.
Globins (hemoglobin, Hb, and myoglobin, Mb) are ferrous
heme-containing, O
2
-binding proteins found widespread in
nature [1,2]. They exhibit an extraordinary range of ligation
rates and affinities, as well as autoxidation rates (conversion
to the nonfunctional ferric hemin) in spite of a highly
conserved folding topology (the Mb fold). The majority of
globins, which consists of % 150 residues, are arranged in a
compact globule consisting of eight (A–H) helices, with the
heme wedged between the E and F helices. A completely
conserved His F8 (eighth residue on helix F) provides the
only covalent bond to the protein, although a conserved
aromatic ring (CD1) (first residue and the loop between
helices C and D) provides considerable stabilization by
p-stacking on the heme [1–3]. Some recently discovered
ÔtruncatedÕ (% 100–120 residues) globins from bacteria
exhibit the general Mb fold but retain only four of the
helices, leaving a largely conserved active site with respect to
more conventional globins [4,5], and one has an unprece-
dented Tyr (CD1) [3]. The modulation of the extreme range
of ligation rates in monomeric globins appears to be
controlled primarily by limited sets of residues on the distal
(opposite side to the proximal His F8) side of PREVIOUS PAGENEXT PAGE
Electric and
Magnetic Fields
FACTS
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10
22
10
20
10
18
10
16
10
14
10
12
10
10
10
8
10
6
10
4
10
2
0
HZ
RadiationIonizing
Gamma
rays
X-rays
Visible
light
60 Hz and
2,450 MHz
(inside oven)
800-
900 MHz
15-30 kHz
and 50-90 Hz
60 Hz
Direct
current
Electromagnetic Spectrum
Frequency is shown in Hertz (Hz). 1 Hz = 1 cycle per
second. (Note that 10
4
means 10x10x10x10 = 10,000
Hz, etc.) kHz = kilohertz = 1000 Hz, MHz = megahertz
= million Hz.
EMF Units
Electric Fields
Usually measured in volts per meter (V/m)
For large elds the units usually used are:
1 kilovolt per meter (kV/m) =
1,000 volts per meter
Magnetic Fields
Usually measured in milliGauss (mG)
Other units sometimes used:
1 microTesla = 10 milliGauss
1 Amp/meter = 0.1257 milliGauss
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1
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E
lectric power lines are familiar to all of us. They have dif-
ferent shapes, different sized poles and varying numbers of
wires. We may not be able to guess how much power they
carry, but we all know what they do: they bring electric power to
our homes and businesses.
Many of the dramatic improvements in health, safety and
quality of life that we benet from today could not have hap-
pened without a reliable and affordable electric supply. But could
electricity be bad for our health? Electric and magnetic elds are
present wherever electricity is used. Do these elds cause cancer
or any other diseases, as some have suggested?
These important and serious questions have been investigated
thoroughly during the past three decades. Several tens of millions
of dollars have been spent worldwide.
Research on EMF still continues because no clear answers
have been found. The balance of scientic evidence to date
indicates that these elds do not cause disease. This discussion
outlines the EMF issue, summarizes the research conducted to
date, and describes what Western Area Power Administration is
doing to address concerns about EMF.
2
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3
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Electric and Magnetic Fields
EMFs are produced both naturally and as a result of human activity. The
earth has both a magnetic eld produced by currents deep inside the molten
core of the planet, and an electric eld produced by electrical activity in the
atmosphere, such as thunderstorms.
A primary characteristic of any eld is the frequency. The frequency
describes how rapidly an electric or magnetic eld oscillates, or cycles back-
ward and forward every second, and is measured in hertz. The earth’s electric
and magnetic elds do not oscillate. They are called static elds and have a
frequency of 0 Hz. Electricity produced in North America produces elds at
a frequency of 60 Hz, or 60 cycles per second, and are known as “extremely
low frequency” or “power frequency” elds. Fields at that frequency carry
very little energy and are only one small part of the electromagnetic spec-
trum that ranges from elds at a frequency of 0 Hz to frequencies in excess
of trillions of Hz. Computers, radios, televisions, cellular telephones, micro-
wave ovens, X-ray equipment and other devices we use daily operate using
frequencies within this
spectrum. The science
and effects of higher
frequency elds are
quite different from
the 60Hz elds this
brochure focuses on.
Power frequency
electric and magnetic
elds occur through hu-
man activity wherever
electricity is generated,
transmitted and used.
The Difference Between Electric and Magnetic Fields
Electric elds
Electric elds are produced by voltage. Voltage is the pressure behind
the ow of electricity. It can be .. .Eddy Currents and Magnetic Damping flux increases, and so an eddy current is set up (Faraday’s law) in the counterclockwise direction (Lenz’s law), as shown Only the right-hand side... Explain why magnetic damping might not be effective on an object made of several thin conducting layers separated by insulation 5/6 Eddy Currents and Magnetic Damping Explain how electromagnetic... currents are to be avoided in conductors, then they can be slotted or constructed of thin layers of conducting material separated by insulating sheets 2/6 Eddy Currents and Magnetic Damping Eddy