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. Arčon, Z. Jagličič, 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. Caldero´n-Moreno, Amılcar 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) 119–124 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. CoeyCarbon 44 , December 2006, Pages 3213-3217 • Carbon–nitrogen 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 Ωm, 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 χ = −170 × 10−9 m3  kg−1 and a small ferromagnetic component of unknown origin with σS of up to 0.2 A m2 kg−1, whereas the soot shows a purely diamagnetic signal, with χ ≈ −40 × 10−9 m3 kg−1

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 5*1018 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 3*10−5 emu or 2.25 emu/cm3 1 FULLERENE = 1 nm, 500 fullerenes = 500 nm, Total number of fullerenes=500 x film square = 8.4e16 Film square = 1.6 e14 fullerenes = 12x12 mm Total weght of fullerenes = 1.65*1.6*0.1*0.1*5e-4=1.3e-6=13 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  nmdiameter) that are interconnected in necklace-like structures. Magnetic measurements ofthe Ag and C nanocomposite, in its powder form, showedweak ferromagnetic behavior up to at least room temperature witha coercive field of 389  Oe at 2  K and 103  Oe at300  K, from which we estimate magnetic ordering up to 425  K.However, pressing the Ag-C powder samples into tablets suppressed theferromagnetism; the pressed samples instead exhibited diamagnetic behavior. Chemical analysiswith EDS and trace metal analysis with ICP-MS indicated thatthere are no magnetic contaminants in the sample. Therefore, weattribute the ferromagnetism to the carbon nanospheres and propose amodel for the observed magnetism. We also measured a pronouncedpeak in the magnetization between 50 and 90  K that wascompletely suppressed when measurements were made upon cooling; we attributethis 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 30–80 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 NKare estimated as 800 K and 0.08, respectively, for K/C 0:035. 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 n=1 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) 119–124 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. 101–102 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 C–C bonds of sp3 sites and located mainly in the interior of the nanocrystals Hydrogen-terminated ND show a high concentration of excess free radicals (up to 1021 spin/g), which are due to dangling C–C 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. Caldero´n-Moreno, Amılcar 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 Curie–Weiss 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-dependent Curie–Weiss 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) 1913–1918 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

23. Island phase 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 themagnetic 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. Arčon, Z. Jagličič, 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 ofpotassium clusters incorporated into zeolite LTA Yasuo Nozue, Tetsuya Kodaira, and Takenari Goto Observation of magnetism in the nanoscale amorphous rutheniumclusters 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. Garcıa, E. Fernandez Pinel, M. Multigner, D. Alca´ntara, 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 - δ filmsSoack Dae Yoon, Yajie Chen, Aria Yang, TrevorGoodrich, 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 oxidesSundaresan, A. , Bhargavi, R, Rangarajan, N., Siddesh, U., Rao, C. N. R.PHYS. REV. B74 161306 2006CeO2, 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 73132404 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) 1–7 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, 646–648 (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