Overview

1
Overview
2
Carbon

• Indirect exchange coupling between magnetic
  adatoms in carbon nanotubes. Costa AT, Kirwan DF,
  Ferreira MS . Phys. Rev. B72 085402 2005 We
  argue that such a long-range character in the
  magnetic interaction can be used in future
  spintronic devices.
• Origin of magnetic moments in carbon nanofoam D.
  Arcon, Z. Jaglicic, A. Zorko, A. V. Rode, A. G.
  Christy, N. R. Madsen, E. G. Gamaly, and B.
  Luther-Davies. Phys. Rev. B 014438 2006
• Magnetic properties of dense graphitic filaments
  formed via thermal decomposition of mesitylene in
  an applied electric field
• Jose M. Calderon-Moreno, Amilcar Labarta,
  Xavier Batlle, Daniel Crespo,Vilas G. Pol, Swati
  V. Pol, Aharon Gedanken CARBON 44 (13) 2864-2867
  NOV 2006 The carbon filaments exhibit
  paramagnetic behavior
• Ferromagnetism induced by heavy-ion irradiation
  in fullerene films. Amit Kumar, D. K. Avasthi, J.
  C. Pivin, A. Tripathi, and F. Singh, PHYSICAL
  REVIEW B 74, 153409 2006
• Novel type of magnetic response in carbon
  nanomaterials. Compernolle, L.F. Chibotaru, A.
  Ceulemans Chemical Physics Letters 428 (2006)
  119124 In strong fields the magnetisation vs.
  field of nanosize molecules becomes strongly
  non-monotonic.
• Magnetic Properties of Hydrogen-Terminated
  Surface Layer of Diamond Nanoparticles. Vladimir
  Osipov, Marina Baidakova, Kazuyuki Takai,
  Toshiaki Enoki, Alexander Vul
• Magnetic properties of CNX whiskers R.D. Gunning
  M. Venkatesan D.H. Grayson and J.M.D. Coey Carbon
  44 , December 2006, Pages 3213-3217
• Very Unusual Magnetic Properties in Multi-walled
  Carbon Nanotube Mats Guo-meng Zhao, Pieder Beeli
  cond-mat/0611110
• Ferromagnetic behavior of carbon nanospheres
  encapsulating silver nanoparticles Caudillo, R.,
  Gao, X. Escudero, R., Jose-Yacaman, M.,
  Goodenough, J. B. PHYSICAL REVIEW B 74 21 Art.
  No. 214418 DEC 2006
• Spintronic properties of carbon-based
  one-dimensional molecular structures Durgun, E.,
  Senger, R. T., Sevincli, H., Mehrez, H.,
  Ciraci, S.
• PHYSICAL REVIEW B 74 23 Art. No. 235413 DEC 200

3
Attempt to repeate Japanese works

• Magnetic properties of CNX whiskers
• R.D. Gunning M. Venkatesan D.H. Grayson and
  J.M.D. Coey Carbon 44 , December 2006, Pages
  3213-3217
• Carbonnitrogen whiskers have been prepared by
  pyrolysis of 1,2-diaminopropane at 950 C or of
  allylamine at 900 C followed by quenching. They
  are scrolls of carbon film typically 250 nm thick
  and up to 1 mm long with about five layers in a
  structure like a cigare russe or brandy snap,
  about 50 µm in diameter. Approximately 8 wt of
  nitrogen is incorporated into the carbon films,
  which are practically amorphous, exhibiting a
  broad diffraction peak at d  0.34 nm. The
  whiskers are on the border of metallic
  conductivity with a resistivity of about 10-6 Om,
  and they may show either a positive or a negative
  temperature coefficient of resistance. The
  pyrolysis produces either whiskers, soot or both.
  Magnetization measurements of the whiskers made
  from 1,2-diaminopropane reveal a large
  diamagnetic susceptibility of ?  -170  10-9 m3 
  kg-1 and a small ferromagnetic component of
  unknown origin with sS of up to 0.2 A m2 kg-1,
  whereas the soot shows a purely diamagnetic
  signal, with ?  -40  10-9 m3 kg-1

4
(No Transcript)
5
5 MV tandem ion-accelerator hosted by the CMAM in
the Universidad Autnoma de Madrid
PIXE experiments performed on some of these
samples always gave concentrations below 10 ppm
of Fe element, and indetectable for other
magnetic impurities.
6
MFM on these proton-irradiated samples, as on
other ones irradiated in air with ion-beam spots
smaller than 100 µm, provided no clear evidence
of magnetic behaviour at the surface of
proton-irradiated regions, in contrast to earlier
re- ports. MOKE experiments performed in the same
samples also gave negative results, always a pure
linear diamagnetic curve was obtained. This is
not too surprising, since the found ferromagnetic
contributions super- imposed on a large
diamagnetic signal are very weak. Moreover, it is
not clear what should be its relative strength at
the supeficial regions probed by
these techniques. In order to improve the layout
of the samples surface to have a better contrast
for MFM studies, we decided to use a grid or mask
of copper.
7
Electron Spin Resonance of Proton-Irradiated
Graphite Kyu Won Lee and Cheol Eui Lee PRL 97,
137206 (2006) the conventional Heisenberg
interaction, i.e., direct (unmediated)
interaction between the localized spins produced
by the proton irradiation, is identified as the
origin of proton irradiation-induced
ferromagnetism in graphite.
How did they make this conclusion if they did not
see any nonlinearity?
8
Ferromagnetism induced by heavy-ion irradiation
in fullerene films Amit Kumar, D. K. Avasthi, J.
C. Pivin, A. Tripathi, and F. Singh, PHYSICAL
REVIEW B 74, 153409 2006
These hystereses are not corrected for the
diamagnetic signal of the Si substrate.
Si
Ar
The ferromagnetic contribution increases with the
ion fluence. When the carbon film is removed by
diamond polishing, the ferromagnetic signal
vanishes. It is worth noting that a small
paramagnetic signal adds to the ferromagnetic one
when the temperature increases. Why pristine film
has nonlinearity? Increase of paramagnetic
signal with temperature is very strange The
saturation magnetization of the film volume of
1.5 x10-5 cm3 reaches 3x10-3 muB/atom for the
fluence of 1013 Si ions/cm2, which is higher than
the magnetization values reported for ion
implanted graphite or diamond The experimentally
determined amount of magnetic impurities were
less than 20 ppm in 5x1018 carbon atoms, .per cm2
for a 500 nm fullerene film, which is equivalent
to 1014 atoms of magnetic impurity. Therefore the
maximum possible contribution to magnetization
due to impurities is less than 10-6 emu, which is
insignificant in comparison to the observed
magnetization 3x10-5 emu or 2.25 emu/cm3 in Si
ion irradiated fullerene films. X-ray
fluorescence analysis was performed to check the
presence of magnetic impurities in as-deposited
pristine and irradiated films, with x-ray
excitation at Punjab University, Chandigarh, and
with proton excitation PIXE at C2RMF, Paris.
These analyses showed that the studied films
contained less than 20 ppm of magnetic metals.
The composition of the samples was also analyzed
by Rutherford Backscattering spectrometry. The
oxygen content in the pristine and irradiated
films were measured by 16Od, p, 17O nuclear
reaction. The film thickness deduced from these
measurements was found to be in good agreement
with that given by quartz thickness monitor. The
films contained oxygen of 1 at. increasing to
10 at. with Si ion fluence. The Ar ion
irradiated fullerene film had about 5 at. of
oxygen. The increase in oxygen is attributed to
dangling bonds created during irradiation, which
on exposure to air pick up oxygen.
9
The experimentally determined amount of magnetic
impurities were less than 20 ppm in 51018 carbon
atoms per cm2 for a 500 nm fullerene film, which
is equivalent to 1014 atoms of magnetic impurity.
Therefore the maximum possible contribution to
magnetization due to impurities is less than 10-6
emu, which is insignificant in comparison to the
observed magnetization 310-5 emu or 2.25 emu/cm3
1 FULLERENE 1 nm, 500 fullerenes 500 nm,
Total number of fullerenes500 x film square
8.4e16 Film square 1.6 e14 fullerenes 12x12
mm Total weght of fullerenes 1.651.60.10.15e
-41.3e-613 microgram 3e-5 emu 0.15 microgram
Fe 1
10
Ferromagnetic behavior of carbon nanospheres
encapsulating silver nanoparticles Caudillo,
R., Gao, X. Escudero, R., Jose-Yacaman, M.,
Goodenough, J. B.  PHYSICAL REVIEW B 74 21
Art. No. 214418 DEC 2006 Ag nanoparticles
encapsulated in carbon nanospheres (10  nm
diameter) that are interconnected in
necklace-like structures.
Magnetic measurements of the Ag and C
nanocomposite, in its powder form, showed weak
ferromagnetic behavior up to at least room
temperature with a coercive field of 389  Oe at
2  K and 103  Oe at 300  K, from which we
estimate magnetic ordering up to 425  K. However,
pressing the Ag-C powder samples into tablets
suppressed the ferromagnetism the pressed
samples instead exhibited diamagnetic behavior.
Chemical analysis with EDS and trace metal
analysis with ICP-MS indicated that there are no
magnetic contaminants in the sample. Therefore,
we attribute the ferromagnetism to the carbon
nanospheres and propose a model for the observed
magnetism. We also measured a pronounced peak in
the magnetization between 50 and 90  K that was
completely suppressed when measurements were made
upon cooling we attribute this peak to a
first-order spin reorientation.
11
We also measured a pronounced peak in the
magnetization between 50 and 90  K that was
completely suppressed when measurements were made
upon cooling we attribute this peak to a
first-order spin reorientation.
12
The potassium accommodated in the nanopores form
clusters consisting of about 60 potassium atoms.
The random potential from the nanographite
domains and nanopore filling effect create
antiferromagnetically interacting localized spins
in the potassium clusters. This results in a new
class of nanomagnetic systems composed of
nonmagnetic elements, which shows novel magnetism
at the high temperature range
13
By considering that the spin density (T value)
for nanographite is independent of the
temperature in the high temperature range, the
contribution of the potassium cluster to the spin
density is obtained by subtracting the T value at
3080 K from the observed T value as shown in
Fig. 3(c). The exponential increase in the T
value for the potassium cluster with an increase
in thetemperature is suggestive of the behavior
of antiferromagnetically fluctuating spin
clusters. The observed magnetism of potassium
clusters is treated based on a simple
antiferromagnetic (AF) cluster model with a
unique spin gap
?E and NK are estimated as 800 K and 0.08,
respectively, for K/C 0035. The values of E and
NK decrease as K/C increases. This means that the
growth in the size of the potassium clusters
tends to reduce both the spin-gap energy and spin
density. The localized spin magnetism of
potassium clusters is attributed to
antiferromagnetically fluctuating
potassium 4s-electron spins.
14
Spintronic properties of carbon-based
one-dimensional molecular structures Durgun,
E., Senger, R. T., Sevincli, H., Mehrez, H.,
Ciraci, S.  PHYSICAL REVIEW B 74 23 Art. No.
235413 DEC 2006 Periodic atomic chains composed
of carbon atoms and 3d transition metal TM atoms
from first-principles methods. Finite-size,
linear molecules made of carbon atomic chains
caped with TM atoms, i.e., TM-C-n-TM structures
are stable and exhibit interesting
magnetoresistive properties.
The indirect exchange interaction of the two TM
atoms through a spacer of n carbon atoms
determines the type of the magnetic ground state
of these structures. The n-dependent n1 to 7
variations of the ground state between
ferromagnetic and antiferromagnetic spin
configurations exhibit several distinct forms,
including regular alternations for Ti, V, Mn, Cr,
Fe, and Co, and irregular forms for Sc and Ni
cases. We present a simple analytical model that
can successfully simulate these variations, and
the induced magnetic moments on the carbon atoms.
Depending on the relative strengths of the carbon
s, p and TM d orbital spin-dependent coupling and
on the on-site energies of the TM atoms there
induces long-range spin polarizations on the
carbon atoms which mediate the exchange
interaction. While periodically repeated TM-C-n
atomic chains exhibit half-metallic properties
with perfect spin polarization at the Fermi
level, finite but asymmetric chains comprising
single, double, and triple TM atoms display
interesting spin-dependent features. These
properties may be altered when these structures
are coupled to electrodes. However, when
connected to appropriate electrodes the TM-C-n-TM
atomic chains act as molecular spin valves in
their ferromagnetic states due to the large
ratios of the conductance values for each spin
type.
15
Novel type of magnetic response in carbon
nanomaterials S. Compernolle, L.F. Chibotaru, A.
Ceulemans Chemical Physics Letters 428 (2006)
119124 We report quantum chemistry
investigations of the magnetic response of large
polycyclic hydrocarbons to a high magnetic field.
In strong fields the magnetisation vs. field of
nanosize molecules becomes strongly
non-monotonic. For nanographenes containing
thousands of atoms this effect develops at ca.
101102 T. It is related to the motion of
vortices in the frontier molecular orbitals and
transformations of ring current patterns. The
described phenomenon is general, in principle
observable in all conjugated planar nanosize
molecules.
16
Magnetic Properties of Hydrogen-Terminated
Surface Layer of Diamond Nanoparticles Vladimir
Osipov, Marina Baidakova, Kazuyuki Takai,
Toshiaki Enoki, Alexander Vul The hydrothermal
treatment induces additional spins (S 1/2) on
the diamond nanocrystal facets and also on the
ribs, where the number of these excess spins
depends roughly linearly on the treatment time
and achieves ca. 40 spins after 36 hours. The
susceptibility behavior suggests the presence of
a strong antiferromagnetic (AFM) coupling between
the surface spins. The appearance of giant
Pauli-like paramagnetic term in the magnetic
susceptibility for the samples treated long time
proves the metallic-like behavior of nanodiamond
surface and the supposition respecting the
appearance of plethora of alternating chains on
the nanocrystal facets before/on the threshold of
the surface reconstruction seems very reasonable.
17
Osipov, Baidakova, Enoki, Takai, Ful. Nan. Car.
Nan 14, 565 2006
Magnetic studies of pristine and
hydrogen-terminated ND samples, obtained by
detonation technique, are reported by Pristine
samples structural defects originating from
dangling CC bonds of sp3 sites and located
mainly in the interior of the nanocrystals Hydroge
n-terminated ND show a high concentration of
excess free radicals (up to 1021 spin/g), which
are due to dangling CC bonds induced on the
surface of diamond nanocrystals by hydrothermal
treatment. Strong antiferromagnetic coupling is
found between the spins localized on the surface.
18
Magnetic properties of dense graphitic filaments
formed via thermal decomposition of mesitylene in
an applied electric field Jose M.
Calderon-Moreno, Amilcar Labarta, Xavier Batlle,
Daniel Crespo,Vilas G. Pol, Swati V. Pol, Aharon
Gedanken CARBON 44 (13) 2864-2867 NOV 2006 The
carbon filaments exhibit paramagnetic
behavior superimposed to the constant
contribution ?0 arising from core and orbital
diamagnetic terms, and Pauli paramagnetic
susceptibility. The total susceptibility at 2 K
was ? 8.4 10-6 emu/g, decreasing up to ? -
6.6 10-7 emu/g at room temperature. The
experimental data in Fig. 4 could be fitted well
by the sum of a temperature-dependent CurieWeiss
term. From the obtained value of the Curie
constant, C 4.023 10-5 emu K/g, and assuming
S 1/2 the localized spin density was estimated
to be NS 6.46 1019 spins/g. This spin density
corresponds to an average separation between
spins of 2.09 nm. The experimental data could
be fitted well by the sum of a temperature-depende
nt CurieWeiss term, C/(T-H), originating from
localized spins and a constant diamagnetic
susceptibility ?0. The obtained value of ?0 was
?0 0.77 10-6 emu/K, about 10 of the value
for bulk graphite. A small negative value of the
Curie temperature W -2.3 K was estimated
19
The dependence of the oriented growth of carbon
filaments on the intensity of a magnetic
field Vilas Ganpat Pol, Swati Vilas Pol, Jose M.
Calderon-Moreno, Mun-Gyu Sung, Shigeo Asai,
Aharon Gedanken, Carbon 44 (2006) 19131918
The large diamagnetic anisotropy of graphitic
clusters and paramagnetism caused by localized
spins at the boundaries rich in graphitic plane
edges must be associated with the observed
magnetic-induced growth. A detailed
characterization of the magnetic properties of
the obtained filaments will help to clarify the
nature of the magnetic interactions and growth
mechanisms. Fig. 1. (a) Perfectly spherical
particles obtained at zero field, (b) SEM images
of carbon spheres carbon filaments prepared at
1 T MF, (c) carbon filaments prepared at 3 T MF,
(d) carbon filaments prepared at 5 T MF, (e)
carbon filaments prepared at 10 T MF, and (f) The
EDX spectra show only the presence of carbon
atoms in all the particles.
20
Very Unusual Magnetic Properties in Multi-walled
Carbon Nanotube Mats Guo-meng Zhao, Pieder Beeli
cond-mat/0611110
21
Non-traditional magnetism
22
(No Transcript)
23
What we want to obtain?
Bulk magnetic carbon
Non-interacting carbon clusters Probably, in
fresh-prepared carbon nanofoam
Non-interacting iron clusters
Interacting carbon clusters?
Interacting impurity atoms
Perfect for nanomedicine
Perfect for spintronics
Questions to the theorists Can we expect
hysteresis in pure carbon system?
24
Indirect exchange coupling between magnetic
adatoms in carbon nanotubes Costa AT, Kirwan DF,
Ferreira MS . Phys. Rev. B72 085402 2005 The
long-range character of the exchange coupling
between localized magnetic moments indirectly
mediated by the conduction electrons of metallic
hosts can play a significant role in determining
the magnetic order of low-dimensional structures.
Here we consider how this indirect coupling
influences the magnetic alignment of adatoms
attached to the walls of carbon nanotubes. A
general expression for the indirect coupling in
terms of single-particle Green functions is
presented. Contrary to the general property that
magnetic moments embedded in a metal display
Friedel-like oscillations in their magnetic
response, calculated values for the coupling
across metallic zigzag nanotubes show monotonic
behavior as a function of the adatom separation.
Rather than an intrinsic property, the
monotonicity is shown to reflect a
commensurability effect in which the coupling
oscillates with periods that coincide with the
lattice parameter of the nanotube host. Such a
commensurability effect does not dominate the
coupling across semiconducting zigzag or metallic
armchair nanotubes. We argue that such a
long-range character in the magnetic interaction
can be used in future spintronic devices.
25
Origin of magnetic moments in carbon nanofoam D.
Arcon, Z. Jaglicic, A. Zorko, A. V. Rode, A. G.
Christy, N. R. Madsen, E. G. Gamaly, and B.
Luther-Davies. Phys. Rev. B 014438 2006 An
impurity analysis of the carbon nanofoam samples
made in different conditions was performed using
inductively coupled plasma-atomic emission
spectroscopy. Samples were digested in a small
volume of hot concentrated nitric acid and then
diluted using ultrapure water. Approximately 0.2
g of foam was digested to produce 20 mL of final
digest, giving an overall dilution factor of
about 100. The digest was then filtered using a
membrane filter to remove particulates and
presented to the spectrometer. A Varian Vista Pro
axial geometry AES was used. The concentrations
of each element measured were calculated from the
intensities of specified atomic emission lines
relative to those in blank 2 itric acid and in a
multielement standard prepared from commercial
single-element standard solutions. Detection
limits in solutions as presented ranged from
single ppb for 3d transition metals, lanthanides
and Mg to tens of ppb for Na, K, Ca, and B-group
metals including Al. Corresponding detection
limits in the foam were therefore hundreds of ppb
to single ppm.
26
Magnetism of nonmagnetic metalsDirect evidence
for ferromagnetic spin polarization in gold
nanoparticles Y. Yamamoto et al cond-mat/0403600
Structure and Magnetization of Small Monodisperse
Platinum Clusters 0.65(5)µB per atom Xiong Liu,
Matthias Bauer, Helmut Bertagnolli, Emil Roduner,
Joris van Slageren,Fritz Phillipp, Phys. Rev.
Lett. 97 253401 2006 Ferromagnetism of potassium
clusters incorporated into zeolite LTA Yasuo
Nozue, Tetsuya Kodaira, and Takenari
Goto Observation of magnetism in the nanoscale
amorphous ruthenium clusters prepared by ion beam
mixing W. C. Wang, Y. Kong, X. He, and B. X. Liu,
Appl. Phys. Lett. 89, 262511 (2006) Permanent
magnetism, magnetic anisotropy, and hysteresis of
thiol-capped gold nanoparticles Crespo P, Litran
R, Rojas TC, Multigner M, de la Fuente JM,
Sanchez-Lopez JC, Garcia MA, Hernando A, Penades
S, Fernandez A PRL 93 087204 2004 The apparent
ferromagnetism is consequently associated with 5d
localized holes generated through Au-S
bonds. Direct evidence for ferromagnetic spin
polarization in gold nanoparticles Y. Yamamoto,
T. Miura, T. Teranishi, M. Miyake, H. Hori M.
Suzuki, N. Kawamura, H. Miyagawa, T. Nakamura, K.
Kobayashi cond-mat/0403600 Fe Impurities Weaken
the Ferromagnetic Behavior in Au Nanoparticles P.
Crespo, M. A. Garcia, E. Fernandez Pinel, M.
Multigner, D. Alcantara, J. M. de la Fuente, S.
Penades, and A. Hernando PRL 97, 177203
(2006) Ferromagnetic behavior observed in
thiolcapped Au NPs cannot be ascribed to the
presence of magnetic impurities, that, opposite
to what is expected, tend to destroy the
ferromagnetic behavior. Chirality-Induced
Spin-Selective Properties of Self-Assembled
Monolayers of DNA on Gold PRL 96, 036101 (2006

27
Magnetism of nonmagnetic oxides Zn, Ti, Cs, In,
Sn, (Hf).
Oxygen-defect-induced magnetism to 880 K in
semiconducting anatase TiO2 - d films Soack Dae
Yoon, Yajie Chen, Aria Yang, Trevor Goodrich, Xu
Zuo, Dario A Arena, Katherine Ziemer, Carmine
Vittoria and Vincent G Harris, J. Phys. Condens.
Matter 18 2006 L355 Same team, Journal of
Magnetism and Magnetic Materials Volume 309,
Issue 2 , February 2007, Pages 171-175.
Ferromagnetism up to 880 K, without the
introduction of magnetic ions Ferromagnetism as a
universal feature of nanoparticles of the
otherwise nonmagnetic oxides Sundaresan, A. ,
Bhargavi, R, Rangarajan, N., Siddesh, U., Rao,
C. N. R. PHYS. REV. B74 161306 2006 CeO2, Al2O3,
ZnO, In2O3, and SnO2. no magnetic impurities
present Again Hf (citing Wang WD, et al. J.
Appl. Phys. 99 08117 2006) RTFM observed in
undoped semiconducting and insulating oxide thin
films TiO2, HfO2, and In2O3 thin films. Defects
and/or oxygen vacancies might be the main source
Hong, Phys. Rev B 73 132404 2006 Fe doping is
not the cause for the FM but only acts as a
catalyst. Removing oxygen enhances the magnetic
moment, while reversibly filling up oxygen
vacancies can destroy the ferromagnetic ordering
of the system. Evidence for magnetism due to
oxygen vacancies in Fe-doped HfO2 thin films
Hong, APL 89 042503 2006
28
Ferromagnetism in doped thin-film oxide and
nitride semiconductors and dielectrics

• Ferromagnetism in doped thin-film oxide and
  nitride semiconductors and dielectrics Chambers,
  Scott A. SURFACE SCIENCE REPORTS 61 (8) 345-381
  OCT 2006 In this Report, the field of
  magnetically doped oxides and nitrides is
  critically reviewed The resulting macroscopic
  magnetic properties are diverse and critically
  dependent on growth and processing conditions
• Ferromagnetism in oxide semiconductors S.A.
  Chambers, T.C. Droubay, C.M. Wang, K.M. Rosso,
  S.M. Heal, D.A. Schwartz, K.R. Kittilstved and
  D.R. Gamelin MATERIALS TODAY 9 (11) 28-35 NOV
  2006
• Ram Seshadri, Current Opinion in Solid State and
  Materials Science 9 (2005) 17 The experimental
  situation on bulk samples strongly favors the
  view that in cases when ferromagnetism is found,
  it is not intrinsic to Zn1-xMxO.
• Activation of high-T-c ferromagnetism in Co2
  TiO2 and Cr3 TiO2 nanorods and nanocrystals by
  grain boundary defects Bryan JD, Santangelo SA,
  Keveren SC, Gamelin DR Gamelin DR, J. Amer. Chem.
  Soc 127 15568-15574 2005 The most important
  factor for activating ferromagnetism is found to
  be the creation of grain boundary defects
• Room-temperature decay and light reactivation of
  high-T-c ferromagnetism in an oxide-diluted
  magnetic semiconductor Pan DY, Wan JG, Xu GL, Lv
  LY , Wu YJ, Min H, Liu JM, Wang GH. J. Amer.
  Chem. Soc. 128 12608 2006 Irradiated magnesium
  oxide TiO2 nanoparticles
• A simple synthesis and magnetic behavior of
  nanocrystalline Zn0.9Co0.1O powders by using Zn
  and Co acetates and polyvinyl pyrrolidone as
  precursors Maensiri S , Laokul P , Phokha S J.
  Magn. Mag. Mat. 305 381 2006 ferromagnetic
  behavior for the ZCO powders
• Observation and manipulation of paramagnetic
  oxygen vacancies in Co-doped TiO2 nanocrystals
  Pan DY, Xu GL, Lv LY, Yong Y, Wang XW, Wan JG,
  Wang GH. Appl. Phys. Lett. 89 082510 2006
• Magnetic properties of epitaxial Co-doped anatase
  TlO2 thin films with excellent structural quality
  Kaspar, T. C., Droubay, T.), McCready, D. E.,
  Nachimuthu, P., Heald, S. M, Wang, C. M., Lea, A.
  S., Shutthanandan, V., Chambers, S. A. Toney, M.
  F.. J. Vac. Sci. Technol.B 24 2012 2006 (uniform
  Co doping, with no evidence of Co segregation or
  secondary phases throughout the film depth or on
  the surface)
• Wang XF, Xu JB, Ke N, Yu JG, Wang J, Li Q, Ong
  HC, Zhang R Appl. Phys. Lett. 88 223108 2006.
  The shallow donorlike defects as the legacy of
  aggregation-based growth were responsible for the
  observed high-temperature ferromagnetism (FM),
  further verifying the recent proposal.
• Kittilstved KR, Liu WK, Gamelin DR Nature Mat. 5
  291 2006 Trends in ferromagnetism across the 3d
  series of TM2 ZnO DMSs

29
Transition metal doped DMS

• Dilute magnetic semiconductors Functional
  ferromagnets Tomasz Dietl News and Views
  Nature Materials 2, 646648 (2003) Semiconductors
  doped with small amounts of magnetic impurities
  such as Mn invariably exhibit room-temperature
  ferromagnetism. But we don't yet understand why
• Dilute magnetic semiconductor nanowires Kulkarni,
  J. S. Kazakova, O., Holmes, J. D.. Appl. Phys. A
  85 277-286 2006 In this review we focus on
  recent advances in the synthesis of DMS nanowires
  as well discussing the structural, optical and
  magnetic properties of these materials
• Room-Temperature Ferromagnetism in a II-VI
  Diluted Magnetic Semiconductor Zn1-xCrxTe H.
  Saito V. Zayets, S. Yamagata, and K. Ando Phys.
  Rev. Lett. 90, 207202 (2003)
• Ferromagnetism below 10 k in Mn-doped BiTe J. W.
  G. Bos, M. Lee, E. Morosan, H. W. Zandbergen, W.
  L. Lee, N. P. Ong, and R. J. Cava1 PHYSICAL
  REVIEW B 74 184429 N 2006
• Magnetism and half-metallicity at the O surfaces
  of ceramic oxides Gallego S, Beltran JI, Cerda J,
  Munoz MC. J. Phys. Cond. Mat 17 L451 2005

30
Pure Si is diamagnetic because it dose not have
a net magnetic moment. Metallic Mn is
antiferromagnetic, with a Néel temperature of
100K. Manganese silicide phases are
antiferromagnetic or nonmagnetic, MnSi has a
Curie temperature of 30 K MnSi1.7 has a Curie
temperatureof 47 K. Only one of the Mn-based
binary oxides is ferromagnetic, with a Curie
temperature of 42 K. It implies that
ferromagnetic ordering of Mn-implanted Si
nanowires at room temperature arises from the
long-range ferromagnetic coupling between
conductive electrons and the distributed Mn
atoms. The results demonstrate the achievement of
a one-dimensional Si-based dilute magnetic
semiconductor.
The increase in magnetization is correlated with
the healing of crystal damages upon annealing. On
the other hand, for 800 C annealed
samples,precipitates were found of Mn3O4 phase.
The decrease in concentration of Mn atoms in Si
NWs led to the weakening of long-range
interactions between Mn atoms.
31
Conclusions

• will be drawn by the project members