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1.
Chemically disordered face-centered cubic (fcc) FePt nanoparticles (NPs) with a mean diameter of 9 nm were synthesized via pyrolysis of iron(III) ethoxide and platinum(II) acetylacetonate. The surface ligands of these NPs were then exchanged from oleic acid to tetramethylammonium hydroxide (TMAOH) to measure the longitudinal (T1) and transverse (T2) proton relaxation times of aqueous dispersion of FePt NPs. Magnetic resonance relaxometry reveals that TMAOH-capped FePt NPs have a higher T2-shortening effect than conventional superparamagnetic iron oxide NPs, indicating that fcc-phase FePt NPs might be superior negative contrast agents for magnetic resonance imaging. 相似文献
2.
In this article, composite nanofibers of poly(ε-caprolactone) (PCL) with iron–platinum (FePt) nanoparticles were successfully fabricated via coaxial electrospinning. The structure and morphology of FePt/PCL composite nanofibers were observed using transmission electron microscope and scanning electron microscope, respectively. The magnetic behavior of FePt/PCL composite nanofibers was investigated by alternating gradient magnetometer at room temperature. 相似文献
3.
D.J. Sellmyer Yingfan XuMinglang Yan Yucheng SuiJian Zhou R. Skomski 《Journal of magnetism and magnetic materials》2006
In this paper we report results on the synthesis and magnetic properties of L10 FePt nanocomposite films. Three fabrication methods have been developed to produce high-anisptropy FePt films: non-epitaxial growth of (0 0 1)-oriented FePt:X (X=Ag, C) composite films that might be used for perpendicular media; monodispersed FePt(CFx) core–shell nanocluster-assembled films grown with a gas-aggregation technique and having uniform cluster size and narrow size distribution; and template-mediated self-assembled FePt clusters prepared with chemical synthesis by a hydrogen reduction technique, which has a high potential for controlling both cluster size and orientation. The magnetic properties are controllable through variations in the nanocluster properties and nanostructure. Analytical and numerical simulations have been done for these films, providing better understanding of the magnetization reversal mechanisms. The films show promise for development as magnetic recording media at extremely high areal densities. 相似文献
4.
FePt (20 nm) films with AgCu (20 nm) underlayer were prepared on thermally oxidized Si (0 0 1) substrates at room temperature by using dc magnetron sputtering, and the films annealed at different temperature to examine the disorder–order transformation of the FePt films. It is found that the ordered L10 FePt phase can form at low annealing temperature. Even after annealing at 300 °C, the in-plane coercivity of 5.2 kOe can be obtained in the film. With increase in annealing temperature, both the ordering degree and coercivity of the films increase. The low-temperature ordering of the films may result from the dynamic stress produced by phase separation in AgCu underlayer and Cu diffusion into FePt phase during annealing. 相似文献
5.
Interlayer exchange coupling in dc-magnetron sputtered Tb29.6Co70.4/FePt bilayers with different annealing temperatures of the FePt film have been investigated. The dependence of ordering degree on perpendicular magnetic properties of the FePt film was studied. The Tb29.6Co70.4/FePt film has high perpendicular coercivity and high saturated magnetization about 7.5 kOe, and 302 emu/cm3, respectively as the substrate temperature is 500 °C and annealing at 500 °C for 30 min. It also shows a strong exchange coupling between this FePt layer and Tb29.6Co70.4 layer. We also examined the interface wall energy in the exchange coupled Tb29.6Co70.4/FePt double layers. 相似文献
6.
S.K. Chen F.T. Yuan W.M. Liao C.W. Hsu Lance Horng 《Journal of magnetism and magnetic materials》2006
High-coercivity Au(60 nm)/FePt(δ nm)/Au(60 nm) trilayer samples were prepared by sputtering at room temperature, followed by post annealing at different temperatures. For the sample with δ=60 nm, L10 ordering transformation occurs at 500 °C. Coercivity (Hc) is increased with the annealing temperature in the studied range 400–800 °C. The Hc value of the trilayer films is also varied with thickness of FePt intermediate layer (δ), from 27 kOe for δ=60 nm to a maximum value of 33.5 kOe for δ=20 nm. X-ray diffraction data indicate that the diffusion of Au atoms into the FePt L10 lattice is negligible even after a high-temperature (800 °C) annealing process. Furthermore, ordering parameter is almost unchanged as δ is reduced from 60 to 15 nm. Transmission electron microscope (TEM) photos indicate that small FePt Ll0 particles are dispersed amid the large-grained Au. We believe that the high coercivity of the trilayer sample is attributed to the small and uniform grain sizes of the highly ordered FePt particles which have perfect phase separation with Au matrix. 相似文献
7.
High density of Sn nanoparticles (NPs) had been obtained directly on Si(0 0 1) substrate by solid phase epitaxy. The dependence of the morphology and crystallinity of Sn NPs on Sn coverage, annealing temperature and annealing time was investigated by atomic force microscope (AFM) and X-ray diffraction (XRD). Uniform and densely packed (∼1010 cm−2) Sn NPs were obtained at low Sn coverage, low annealing temperature and short annealing time, respectively. The XRD results showed that, the formed Sn NPs were in the form of crystalline β-Sn, with a distinct orientation of Sn(1 1 0)//Si(0 0 1). The nucleation activation energy of Sn adatoms on Si(0 0 1) surface was estimated to be 0.41 ± 0.05 eV. 相似文献
8.
A.C. Sun Y.C. Tsai Jen-Hwa Hsu P.C. Kuo H.L. Huang 《Journal of magnetism and magnetic materials》2008
(Fe48Pt52)100−x–(MgO)x films were used to examine the performance of a perpendicular percolated medium. Two underlayers, Pt(0 0 1)/Cr(0 0 2) and MgO(0 0 2), were used for comparison. The (Fe48Pt52)100−x–(MgO)x film with the MgO underlayer exhibits a strong preference to segregate at FePt grain boundaries. The microstructure with small closely packed MgO particles (2–4 nm) dispersed uniformly in the L10 FePt matrix was achieved in the Pt/Cr underlayered sample. Structural data reveal that the precipitate is crystallographically coherent with the surrounding L10 FePt phase and preserves good lattice alignment. Magnetic results indicate significant pinning behavior for those introduced non-magnetic columns with an enhanced coercivity of about 70%—much greater than that of the MgO underlayered samples. Percolated perpendicular medium can be realized in the FePt system and a Pt(0 0 1)/Cr(0 0 2) underlayer promotes the formation of pinning sites within the FePt grains. 相似文献
9.
Luminescence properties of Eu3+ doped TeO2-PbO-GeO2 glasses containing gold nanoparticles (NPs) were investigated. The emission spectra of the samples exhibited enhancement of Eu3+ luminescence due to the presence of gold NPs. The emission at 614 nm, due to the Eu3+ hypersensitive transition 5D0-7F2, is much influenced by the gold NPs and increases by ≈100% for samples heat-treated at 350 °C during 41 h. 相似文献
10.
Qitu Hu Zibao Gan Xiuwen Zheng Aihua Zhao Xu Zhang 《Journal of nanoparticle research》2011,13(8):3191-3197
High-density attachment and one-dimensional (1D) array of FePt nanoparticles (NPs) along carbon nanotubes (CNTs) surface to
generate FePt/CNT nanocomposites were successfully obtained via a facile CNT-mediated microwave polyol method. The as-prepared
1D FePt/CNTs is about 10–20 nm in diameter and up to μm scale in length. By adjusting the solvents, the ratio of Fe/Pt and
the attached density of FePt NPs on the surface of CNTs could be well controlled. The structures, composition, and magnetic
properties of the FePt/CNTs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution
transmission electron microscopy (HRTEM), and magnetic measurements. The possible growth mechanism has also been proposed. 相似文献
11.
Using hexamethyldisiloxane (HMDSO) monomer, the magnetic nanoparticles (NPs) of nickel oxide (NiO) were modified by using an atmospheric room-temperature plasma fluidized bed (ARPFB). The plasma gas temperature of the ARPFB was not higher than 325 K, which was favorable for organic polymerization. The plasma optical emission spectrum (OES) of the gas mixture consisting of argon (Ar) and HMDSO was recorded by a UV-visible monochromator. The as-treated NPs were characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the assembling NPs were isolated greatly after modified by the organosilicon polymer. Moreover, this treatment process changed the wettability of the NPs from super-hydrophilicity to super-hydrophobicity, and the contact angle (CA) of water on the modified NPs surface exceeded 150°. Therefore, the ARPFB is a prospective technology for the NPs surface modification according to the different requirements. 相似文献
12.
Colloidal CdSe nanoparticles (NPs), passivated with CdS and ZnS, were characterized by resonant Raman scattering and photoluminescence (PL). The effect of the passivating shell, its volume and formation procedure on optical and vibrational spectra is discussed. Analyzing the Raman peaks due to optical phonons inside the core and those related to the core-shell interface allows some understanding of the relation between the core-shell structure and its PL properties to be achieved. In particular, a compositional intermixing at the core/shell interface of the NPs was deduced from the Raman spectra, which can noticeably affect their PL intensity. 相似文献
13.
Vladimir Krivoruchko Tat’yana KonstantinovaAnton Mazur Andrey ProkhorovVictor Varyukhin 《Journal of magnetism and magnetic materials》2006
Using a co-precipitation method, perovskite-type manganese oxide La0.7Sr0.3MnO3 nanoparticles (NPs) with particle size 12 nm were prepared. Detailed studies of both 55Mn nuclear magnetic resonance and superparamagnetic resonance spectrum, completed by magnetic measurements, have been performed to obtain microscopic information on the local magnetic structure of the NP. Our results on nuclear dynamics provide direct evidence of formation of a magnetically dead layer, of the thickness ≈2 nm, at the particle surface. Temperature dependences of the magnetic resonance spectra have been measured to obtain information about complex magnetic properties of La0.7Sr0.3MnO3 fine-particle ensembles. In particular, electron paramagnetic resonance spectrum at 300 K shows a relatively narrow sharp line, but as the temperature decreases to 5 K, the apparent resonance field decreases and the line width considerably increases. The low-temperature blocking of the NPs magnetic moments has been clearly observed in the electron paramagnetic resonances. The blocking temperature depends on the measuring frequency and for the ensemble of 12 nm NPs at 9.244 GHz has been evaluated as 110 K. 相似文献
14.
W.B. Mi 《Applied Surface Science》2006,253(4):1830-1835
N-doped FePt-C nanocomposite films were fabricated using facing-target sputtering method under different N2 partial pressures (PN) at room temperature. Annealing at 650 °C turns the amorphous films into ordered structures. Nitrogen doping not only make the ordering of FePt particles easier than the ordering in FePt-C films, due to the enhanced diffusivity of Fe and Pt atoms, but also effectively limits the growth of the FePt particles during the thermal induced ordering, especially for the annealed films fabricated at PN = 40%, where the average size of well-isolated FePt particles is only ∼8 nm. The particle size reduction and the enhanced diffusion of Fe and Pt atoms can be ascribed to the desorption of doped N atoms and dissociation of FeN bonds during annealing. The room-temperature coercivity of the samples decreases with the PN due to the particle size reduction and thus the enhancement of the thermal agitation for small particles during the magnetizing procedure. 相似文献
15.
D.H. Wei T.S. Chin K.L. You C.C. Yu Y. Liou Y.D. Yao 《Journal of magnetism and magnetic materials》2006
L10-ordered FePt thin films prepared by molecular-beam epitaxy on MgO (0 0 1) substrate at 320 °C with different thickness of Pt buffer layer have been investigated. The out-of-plane coercivity increases with increasing thickness of Pt buffer. The maximum values of the long-range order parameter and uniaxial magnetic anisotropy energy are 0.72 and 1.78×107 erg/cm3, respectively, for films with 12 nm thick Pt buffer layer, where the c/a ratio (0.976) shows the minimum value. The reason for the enhancement in ordering is due to the proper lattice strains Pt buffer bestows on FePt layer, these strains are equal to the contraction in lattice parameter c and the expansion in a. Studies of angular-dependent coercivity revealed that the magnetization reversal behaviour shifts from a domain-wall motion dominated case towards a near rotational mode with increasing thickness of Pt buffer layer. 相似文献
16.
采用脉冲激光沉积法,在MgO(100)面上外延生长了FePt:MgO多层纳米复合薄膜,FePt成分为Fe48Pt52.FePt纳米颗粒周期性嵌埋于单晶MgO外延层中.原位反射式高能电子衍射分析结果表明,MgO外延层呈层状生长,而FePt纳米颗粒呈岛状生长.在整个FePt:MgO纳米复合薄膜的生长过程中,成功实现了层状-岛状生长模式的交替控制.高分辨透射电子显微镜分析结果表明,退火热处理后,结晶完整的L10-FePt纳米颗粒粒径约为5 nm,呈扁平六角形状,在MgO基底上形成逐层排列的纳米点阵.磁滞回线结果表明,退火后薄膜矫顽力增大,有序度提高,磁性增强. 相似文献
17.
A systematic study of the magnetic properties by ion beam sputter-deposition system, was conducted in conjunction with the structure of FePt/FeMn multilayers fabricated onto MgO(0 0 1) substrates. Both parallel and perpendicular exchange biases were observed in the multilayers and were found to decrease drastically, as the deposition temperature is higher than 350 °C, which is evidently due to the interdiffusion at the interface. The thickness dependence study shows that the perpendicular magnetic anisotropy observed in the multilayers originates from surface anisotropy, being consistent with the decrease of perpendicular magnetic anisotropy as the deposition temperature is increased. The difference between parallel and perpendicular blocking temperatures that was clearly observed, is possibly due to the spin canting out of plane at the interface. 相似文献
18.
FePt and FePt/Cr films were epitaxially grown on MgO (2 0 0) substrates at 350 °C by DC magnetron sputtering. The structural properties and epitaxial relationship are investigated by high-resolution X-ray diffraction (XRD). The XRD spectra revealed that both FePt and FePt/Cr films had a (0 0 1) preferred orientation. However, FePt films with Cr underlayers had a larger a and a smaller c than those of the samples without Cr underlayers. Furthermore, the FePt (0 0 1) peak characterized by its rocking curves became less pronounced when the Cr underlayer was applied. The off-spectra from the MgO (1 1 1), Cr (1 0 1) and FePt (1 1 1) demonstrated that the epitaxial relationship between the FePt film, Cr underlayer and MgO substrate was confirmed to be FePt (0 0 1)<100> || Cr (1 0 0)<1 1 0> || MgO (1 0 0)<0 0 1>. The domain size and Ms decreased when the Cr underlayer was applied due to the diffusion of Cr and the existence of the initial layer between Cr and FePt layers. 相似文献
19.
S.C. Chen P.C. Kuo A.C. Sun C.Y. Chou Y.H. Fang T.H. Wu 《Journal of magnetism and magnetic materials》2006
An in-plane magnetic anisotropy of FePt film is obtained in the MgO 5 nm/FePt t nm/MgO 5 nm films (where t=5, 10 and 20 nm). Both the in-plane coercivity (Hc∥) and the perpendicular magnetic anisotropy of FePt films are increased when introducing an Ag-capped layer instead of MgO-capped layer. An in-plane coercivity is 3154 Oe for the MgO 5 nm/FePt 10 nm/MgO 5 nm film, and it can be increased to 4846 Oe as a 5 nm Ag-capped layer instead of MgO-capped layer. The transmission electron microscopy (TEM)-energy disperse spectrum (EDS) analysis shows that the Ag mainly distributed at the grain boundary of FePt, that leads the increase of the grain boundary energy, which will enhance coercivity and perpendicular magnetic anisotropy of FePt film. 相似文献
20.
The microstructure and magnetic properties of FePt films grown on Cr and CrW underlayers were investigated. The FePt films that deposited on Cr underlayer show (2 0 0) orientation and low coercivity because of the diffusion between FePt and Cr underlayer. The misfit between FePt magnetic layer and underlayer increases by small addition of W element in Cr underlayer or using a thin Mo intermediate layer, which is favorable for the formation of (0 0 1) orientation and the transformation of FePt from fcc to fct phase. A good FePt (0 0 1) texture was obtained in the films with Cr85W15 underlayer with substrate temperature of 400 °C. The FePt films deposited on Mo/Cr underlayer exhibit larger coercivity than that of the films grown on Pt/Cr85W15 because 5 nm Mo intermediate layer depressed the diffusion of Cr into magnetic layer. 相似文献