| 1. |
- Fang, Mei, 1984-, et al.
(författare)
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Co-precipitation of iron oxide nanoparticles by rapid mixing
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Synthesis of Magnetite appears to be a topic of continued interest because of its versatility and the variety applications. Among the chemical techniques to synthesize Fe3O4, co-precipitation approach although very common, seems to be extremely sensitive to the consequences of nucleation, growth and most of all the rate of the reaction involved. This work is an attempt to demonstrate the complexities of obtaining monodispersed nanosized Fe3O4 particles. We consider the role of rapid mixing and its consequences on co-precipitation at ice-point, room temperature and boiling water temperatures on the magnetic properties of Fe3O4. We obtained crystallites varying in the range from 6.6 nm (grown in ice-water) to 7.9 nm (grown in boiling water) as determined from the broadening of XRD diffraction peaks using the Scherrer approach. With the increase of the particle size, the saturate magnetization of iron oxides increases from 52 emu/g to 63 emu/g, and the coercivity increases from 0.5 Oe to 7.9 Oe. Layers of nanosized magnetic particles on glass substrates show unusual wavelength dependence of Faraday rotation loops which show a reversal phenomenon in the sign of the magnetization around 550.
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| 2. |
- Kapilashrami, Mukes, et al.
(författare)
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Coexistence of ultraviolet photo-response and room-temperature ferromagnetism in polycrystalline ZnO thin films
- 2010
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Ingår i: Materials letters (General ed.). - : Elsevier BV. - 0167-577X .- 1873-4979. ; 64:11, s. 1291-1294
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Tidskriftsartikel (refereegranskat)abstract
- The coexistence of ultraviolet (UV) photoconductivity (PC) and room-temperature ferromagnetism (RTFM) is observed in polycrystalline ZnO thin films deposited by unbalanced magnetron sputtering under high oxygen pressure. A significant increase in PC (similar to 870% to 40000%) is observed with increasing film thickness and the consequent structural disorder and film porosity. In contrast, the saturation magnetization (M(S)) at room temperature is found to decrease from 1.02 emu/g to 0.53 emu/g with increasing film thickness from 50 to 150 nm.
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| 3. |
- Lee, Sangmin, et al.
(författare)
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Magneto-Thermo-Gravimetric technique to investigate the structural and magnetic properties of Fe-B-Nb-Y Bulk Metallic Glass
- 2009
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Ingår i: 13TH INTERNATIONAL CONFERENCE ON RAPIDLY QUENCHED AND METASTABLE MATERIALS. - : IOP Publishing. ; , s. 012074-
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Konferensbidrag (refereegranskat)abstract
- Magneto-thermo-gravimetric (MTG) technique is highly informative about the changes in the magnetic state, as well as structural changes in a system, which cannot be often noticed in calorimetric measurements. We demonstrate the versatility of this technique in determining the magnetic transition temperature, and the subsequent crystallization process in a (Fe(0.72)B(0.24)Nb(0.04))(95.5)Y(4.5) Bulk Metallic Glass (BMG). MTG and DSC analyses were carried out at the heating rate of 0.67 K/s from RT similar to 1170 K. As a result of the repeated MTG measurements, a magnetic 2(nd) amorphous phase was observed in the BMG sample, which could be the first measurement for the Magnetic Short Range Ordering (MSRO). Consequently, the MTG measurement is proved as the most convenient method for determining the various structural and magnetic transitions in a glassy material.
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| 4. |
- Masood, Ansar, et al.
(författare)
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A New Class of Materials for Magneto-Optical Applications : Transparent Amorphous Thin Films of Fe-B-Nb and Fe-B-Nb-Y Metallic Glassy Alloys
- 2014
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:4, s. 4004005-
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Tidskriftsartikel (refereegranskat)abstract
- Optically highly transparent, soft magnetic thin films (4-18 nm thick) of Fe-B-Nb- and Fe-B-Nb-Y-based glassy metal targets were grown on quartz substrates by pulsed laser deposition, and their optical and magneto-optical properties were investigated over the visible spectrum (400-700 nm). All the films found to be fully amorphous in structure were continuous with uniform thickness and surface morphology. Their optical transmittance in the range 50%-85% was found to be film thickness dependent over the entire visible regime. The Verdet constant (V) and Faraday rotation angle (theta(f)) for different films (similar to 4-18 nm) investigated as a function of wavelength (lambda) show considerably higher values for the films of Fe-B-Nb-Y alloy as compared with those for Fe-B-Nb films, e. g., the similar to 4 nm film of Fe-B-Nb-Y alloy exhibits V similar to 49 degrees/Oe cm and theta(f)similar to 26 degrees/mu m while it decreased to similar to 29.4 degrees/Oe and similar to 11.8 degrees/mu m, respectively, for the Fe-B-Nb alloy at lambda=611 nm. A linear relationship is found for the wavelength dependence of V and theta(f) for both alloy systems. To the best of our knowledge, these values are considerably higher than those reported for any other magneto-optic material. The films are found to be soft magnetic with a high saturation moment while their magnetic coercivity values increases with thinness of the films. The observed combination of optical and magneto-optical properties of this new class of amorphous metallic films makes them viable for multifunctional magneto-optical applications.
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| 5. |
- Wu, Yan, et al.
(författare)
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Enhanced Photoresponse of Inkjet-Printed ZnO Thin Films Capped with CdS Nanoparticles
- 2010
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 1:1, s. 89-92
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Tidskriftsartikel (refereegranskat)abstract
- Composite semiconductors provide routes for realizing high-performance electronic devices, but for many applications of such devices, low-cost manufacturing techniques are desirable. We have engineered a 3 orders of magnitude enhancement of the ultraviolet photoresponse of ZnO thin films, fabricated "in situ" by drop-on-demand inkjet printing, and then capped with CdS nanoparticles by dip. coating. As a consequence, the decay time of the photoresponse is. reduced to about 4 ms. Thus, capping with CdS not only suppresses the detrimental passivation layer of ZnO thin films, but also generates an interfacial carrier transport layer to reduce the probability of carrier recombination.
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| 6. |
- Wu, Yan, et al.
(författare)
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Enhanced photoresponse of inkjet printed ZnO thin films induced by chemically capped CdS nanoparticles by dip coating
- 2009
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 7402, s. 740207-
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Tidskriftsartikel (refereegranskat)abstract
- Monodispersed CdS nanoparticles (NP) are dip coated on porous ZnO thin film deposited by inkjet printing. Optical absorption characteristics of the composite films show that the composite exhibits two main peaks centered at 355 nm due to the absorption at UV region from ZnO, and 433 nm arising from CdS NP. On UV radiations the electrical conductivity of CdS/ZnO composite thin film with 5 dip cycles is found to be enhanced more than three orders magnitude compared with that of the ZnO which we attribute to be the effect of interfacial charge transfer. Also, the UV photoresponse of ZnO shows pronounced enhancement after CdS capping.
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| 7. |
- Wu, Yan, et al.
(författare)
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Room Temperature Ferromagnetism and Fast Ultraviolet Photoresponse of Inkjet-Printed Mn-Doped ZnO Thin Films
- 2010
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 46:6, s. 2152-2155
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Tidskriftsartikel (refereegranskat)abstract
- We have synthesized Mn-doped ZnO thin films by inkjet printing using a two-step annealing process at 200 C for the decomposition of the organic compounds, and at various temperatures above 400 degrees C to tailor room temperature ferromagnetism. Highly c axis oriented 80 to 400 nm thin films on ( 001) Si substrates are obtained with a magnetic moment as large as 2.1 mu(B)/Mn2+. X-ray absorption and emission spectra measurements at the O K edge and the Mn L edge suggest strong p-d hybridization between the Mn2+ and O2-. Furthermore, Mn L edge XAS indicates the emergence of Mn3+ /Mn4+ mixed valence states for films annealed above 500 degrees C that leads to suppression of ferromagnetic ordering. All of these films show large and fast ultraviolet (UV) photoresponse with the decay times of about 0.5 ms, suggesting the potential for designing multifunctional UV sensors.
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