bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micromagnetic simulation of critical fields of rectangular and elliptical cells for the toggle‐mode magnetic random access memory
Authors: Kim K. S. , Lim S. H. 
Published: December 2007

AbstractA micromagnetic simulation is carried out to examine the effects of the shape of exchange‐coupled trilayer cells on the magnetization switching behavior, in an effort to reduce the switching field in the toggle‐mode magnetic random access memory. Two different shapes of rectangular and elliptical cells are considered. The switching behavior of the elliptical cells shows a qualitative agreement with the single domain model for 3D ellipsoids. However, the magnetization‐flop field differs significantly, except for the small aspect ratio and the thickness asymmetry of the two magnetic layers. For the rectangular cells, the switching behavior differs significantly, particularly at a small aspect ratio, due to very strong demagnetizing fields, causing to form end domains. As the aspect ratio increases, the magnetization‐flop field increases while the saturation field decreases. This opposite dependence of the two critical fields on the aspect ratio results in the decrease in the write window margin with increasing aspect ratio. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Giant magnetoimpedence effects in micro‐patterned Co52Fe32B11Si5 amorphous ribbons
Authors: Park Sun Hee , Chun Dong Won , Han Jun Hyun , Kim Young‐Ho , Jeung Won Young 
Published: December 2007

AbstractWe report the giant magnetoimpedence (GMI) effect in Co52Fe32B11Si5 amorphous ribbon micro‐patterned using photolithography and wet etching process. The effects of AC frequency and amplitude on GMI characteristics are investigated in our micro‐patterned GMI devices. Furthermore, it is shown that thickness of patterned ribbon plays a significant role on the GMI behaviour and response condition of AC frequency and amplitude. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nondestructive testing for metallic flaws using inductive coil sensor with circular typed single loop excitation coil
Authors: Kim Ki Hyeon , Lee Jun Sik , Kim Nanyong , Jang Doguen , Kim Young Ho , Kim Jongryoul 
Published: December 2007

AbstractAC magnetic field was used for the detection of flaws on surface of the conductive specimens. The nondestructive sensor probe was composed of the magnetic yoke coil as a sensing component and exciting single line coil. The excitation coil generated the AC magnetic fields with the frequency of around 27 kHz which were applied to the specimen with artificial flaws. The specimens were prepared with the various shape (slit and hole), size (minimum depth and width; 0.5 mm) of artificial flaws on each of material (Al, Cu; nonmagnetic metal, Fe, FeC; magnetic metal), respectively. The signal for the positions and shapes of surface flaws on metallic specimens were detected with high sensitivity with signal to noise ratio of over 15 by the magnetic yoke typed search coil. The images of flaws were obtained by measured output signal, which results were good coincidence with real flaws. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exchange coupling in FePt‐FePt3 nanocomposite films
Authors: Lin K.‐W. , Guo J.‐Y. , Liu C.‐Y. , Ouyang H. , van Lierop J. , Phuoc N. N. , Suzuki T. 
Published: December 2007

AbstractIn this study, the structural and magnetic properties of exchange coupled nanocomposite FePt‐FePt3 films were investigated. X‐ray diffraction and transmission electron microscopy results showed that after rapid thermal annealing (600 °C for 6 minutes), a phase transformation from [Pt+Fe] into composite FePt‐FePt3 phases was obtained. Annealing created an ordered FePt phase that resulted in a large room temperature coercivity (Hc ∼ 3200 Oe) compared to the as‐deposited film (Hc ∼ 20 Oe). While no exchange bias field (Hex ∼ 0 Oe) was measured at room temperature, the annealed sample showed significant Hex ∼ ‐500 Oe at lower temperatures (150 K ≤ T ≤ 250 K), indicative of exchange coupling between FePt and FePt3. The high blocking temperature (∼250 K) indicates FePt3 exhibits an enhanced Néel temperature. Further increasing the annealing temperature to 700 °C resulted in a reduction of Hex which is attributed to the transformation of FePt3 into the FePt phase at this higher annealing temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of transient annealing on patterned CoFeB‐based magnetic tunnel junctions
Authors: Wu Kuo‐Ming , Huang Chao‐Hsien , Lin Shiao‐Chi , Kao Ming‐Jer , Tsai Ming‐Jinn , Wu Jong‐Ching , Horng Lance 
Published: December 2007

AbstractIn this study, the transient annealing effect on the switching behavior of microstructured Co60Fe20B20‐based magnetic tunnel junctions has been studied through magnetoresistacne measurements (R‐H loop). Elliptical shape of devices with long/short axis of 4/2 micrometers was patterned out of sheet film stack of: Ta (20)/ PtMn (15)/ CoFeB (3)/ Al (0.7)‐oxide/ CoFeB (2)/ Ru (8)/ Ta (40) (thickness unit in nanometers) after a conventional long time field cooling annealing. The transient annealing was then executed by sample loading into a furnace with pre‐set temperatures ranging from 100 to 400 °C for only 5 minutes in the absence of any external magnetic field. The vortex‐like reverse of free layer in as‐etched MTJ evidently changes to single‐domain‐like reverser after 200∼250 °C transient annealing. The magnetoresistance was found to increase with increasing annealing temperatures up to 265 °C and then slowly decrease at higher annealing temperatures. The transient thermal annealing creates obvious efforts to repair magnetic properties of MTJ cell befor 265 °C annealing and results in less damage at temperature of 350 °C and 400 °C. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coating of magnetic particle with polystyrene and its magnetorheological characterization
Authors: Kim Yoon Hee , Park Bong Jun , Choi Hyoung Jin , Seo Yongsok 
Published: December 2007

AbstractMagnetic composite particles were prepared via dispersion polymerization of styrene in the presence of γ‐Fe2O3 nanoparticles. The fabricated magnetic composite nanoparticles were dispersed into non‐magnetic suspending media to be adopted for magnetorheological (MR) fluid, whose rheological properties can be drastically changed in the external magnetic field. The MR efficiency of γ‐Fe2O3/polystyrene composite based fluid was examined by a rotational rheometer equipped with a magnetic field supplier. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polymeric nanobead coated carbonyl iron particles and their magnetic property
Authors: Fang Fei Fei , Choi Hyoung Jin 
Published: December 2007

AbstractMagnetic carbonyl iron (CI) particles have attracted great attention due to their high saturation magnetization and appropriate particle size for magnetorheological (MR) materials. However, hydrodynamic instability of the CI particle suspension which was attributed to the large density mismatch between the dispersed CI particles and the medium has affected its predominant role for MR applications. A novel magnetic CI/polystyrene (PS) composite with nano‐scaled PS spheres sprinkled on the surface of the CI particles was fabricated via a normal dispersion polymerization in this work. Physical properties, MR behaviors as well as the improvement in sedimentation problem were investigated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromagnetic study of magnetization reversal in patterned DyFeCo thin films
Authors: Lee Ching‐Ming , Ye L. X. , Lee J. M. , Wu Te‐Ho 
Published: December 2007

AbstractMagnetization reversal in patterned perpendicular anisotropic DyFeCo films was investigated using micromagnetic simulations. The model consists of a square film of dimension 1 μm × 1 μm × 50 nm and a circular hole of diameter 500 nm on the top surface, with depth varying from 0‐30 nm. The results show that for shallower holes the coercivity decreases rapidly with the hole depth, but for the deeper holes, the coercivity in the hole region is much larger than in the land region. Further analysis indicates the variation in coercivity is due to the narrow transition region formed near the hole boundary where the magnetization has a tilted distribution determined mainly by the competition between anisotropy and exchange interactions. The simulation results are qualitatively consistent with our previous experimental outcome. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐frequency noise absorbing properties of nickel nanowire arrays prepared by DC electrodeposition
Authors: Jeong Jong‐Hyun , Kim Sun‐Hong , Min Ji Hyun , Kim Young Keun , Kim Sung‐Soo 
Published: December 2007

AbstractNickel nanowire arrays are fabricated by electrochemical deposition in highly ordered nanosized pores in AAO (anodized aluminum oxide) templates, and their static and high‐frequency noise absorbing properties have been investigated. Using the channelled AAO templates, a nickel nanowires array was fabricated by DC electrodeposition. Magnetic hysteresis was observed with a coercivity of 250∼300 Oe depending on the field orientation with respect to wire axis. Noise absorbing properties of the nickel nanowires array was measured using the microstrip line. S11 parameter increases with frequency and reaches a saturated value of about ‐10 dB. The reflected power (about 10%) is much less than that of nickel thin film (about ‐3 dB), which is due to higher in‐plane electrical resistance of the nanowire array structure. S21 decreases with frequency and has a value of ‐3 dB at 2 GHz. The attenuation of conduction noise through microstrip line is due to the magnetic loss of individual nickel nanowires. Power absorption of the Ni nanowire array was estimated to be 50% in the frequency range above 2 GHz. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructure study of the Co‐added FePt thin films with high energy density
Authors: Yuan F. T. , Hsiao H. N. , Chen S. K. , Chang H. W. , You K. L. , Yao Y. D. 
Published: December 2007

AbstractMicrostructure, crystal structure, and magnetic properties of the Fe49–xCoxPt51 (x = 0, 0.7, 1.3, 2.2) thin films deposited on glass substrates were investigated. The addition of Co was found to enhance the magnetization of the FePt L l0 phase, thus increases the energy product, (BH)max. A maximum value of (BH)max of 18.4 MGOe was obtained in the sample with x = 1.3 annealing at 500 °C. The microstructure results indicated that significant grain refining was found in the x = 2.2 sample, which reduced from averagely 60 nm for the x = 0.0∼1.3 sample to 30 nm. The concentration of Co was uniform in the Fe‐Pt‐Co film except x = 1.3 film, in which small grains with 10∼20 nm in diameter showed higher percentage of Co. Corresponding to the compositional inhomogeneity, X‐ray structural analysis revealed that the x = 1.3 film contained about 20 vol.% disordered fcc phase, which was much higher than the other composition samples (<7 vol.%). The exchanging coupling between the ordered and disordered phase can explain the enhanced magnetic properties. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic pinning‐effect in Nd0.7Ca0.3MnO3/YBa2Cu3O7 bilayer
Authors: Hsu Daniel , Lin J. G. , Wu W. F. 
Published: December 2007

AbstractThe vortex lines of superconductor can be driven by electrical currents, which are often coupled with a reliable control of flux quanta movement by defects or magnetic domains. In this work, the magnetic pinning‐effect in Nd0.7Ca0.3MnO3/YBa2Cu3O7 (NCMO/YBCO) bilayers is investigated. It is found that by increasing the field from 0 to 5 Tesla, the critical current Ic of pure YBCO film at 50 K is suppressed by three orders of magnitude. However, in the NCMO/YBCO bilayer Ic is less sensitive to the field and maintains at the level of 100 mA at high field. This result indicates that the magnetic pining effect of NCMO is much more efficient than the conventional routes, which maybe related to the fine domain structure of NCMO film. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Compensation of native defects in PbTe and Pb1–xSnxTe
Authors: Babentsov V. N. , Sizov F. F. 
Published: December 2007

AbstractSemi‐insulation of the narrow‐gap IV–VI semiconductor compounds PbTe and Pb1–xSnxTe used for infrared optoelectronic applications was investigated technologically and theoretically. Practically important cases in which the concentration of native defects greatly exceeds the intrinsic concentra‐ tion of free carriers due to the growth conditions are discussed. In particular, doping conditions for the semi‐insulation are determined for Cd, In and Ga compensating impurities. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optically and electrically induced dissipation in quantum Hall systems
Authors: Nachtwei G. , Stellmach C. , Vasile G. , Hein G. 
Published: December 2007

AbstractWe have studied the onset of dissipation in quantum Hall systems (QHSs), patterned in various geometries (Hall bars, meanders and Corbino rings) from wafers with heterojunctions (GaAs/GaAlAs) and HgTe quantum wells with adjacent HgCdTe barriers. The QH samples were excited by electrical pulses with pulse durations tP of 0.5 ns ≤ tP ≤ 180 ns or by illumination with electromagnetic waves of 1.7 THz ≤ f ≤ 2.5 THz. These waves were either emitted coherently by a pulsed p‐Ge laser system or by a thermal source. In the case of excitation by electric pulses, it is necessary to exceed a certain critical pulse length $ t ^{\rm c}_{\rm P} $ which is a function of various extrinsic parameters and sample properties. For $ t _{\rm P} < t ^{\rm c}_{\rm P} $ no dissipation occurs inside the QHSs. Also, using THz illumination, the QHSs can be driven to dissipation. We found different mechanisms to be responsible for the photoresponse (PR) of the QHSs: non‐resonant (bolometric) and resonant (cyclotron resonance) contributions to the PR of the QHSs. First attempts to develop a quantitative model for the observed data are made. We are able to describe a part of the observations by either a drift model or a two‐level model. The quantitative agreement of these calculations with the measured data is, however, limited. This is due to the simplicity of the models applied so far and to the complex behaviour of QHSs when nonlinearly excited. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of electronic transport in the integer quantum Hall regime
Authors: Hohls Frank , Sukhodub Gennadiy , Haug Rolf J. 
Published: December 2007

AbstractWe examine different aspects of the dynamics of electronic transport in the integer quantum Hall effect. In the first part the quantum Hall plateau transition is studied. We present experimental results which confirm a universal scaling behaviour near the critical point of this quantum phase transition between adjacent quantum Hall phases. The second part focuses on the transport properties of quantum Hall edge channels. We use selective detection of individual channels to proof the existence of an inter‐edge magneto plasmon mode. Furthermore we study the equilibration between spin polarised edge channels at very high magnetic fields. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Penetration depth anisotropy in cuprates with pseudogap
Authors: Ghosh Angsula 
Published: December 2007

AbstractWe study the penetration depths along the a (λa), b (λb) and c (λc)‐axes in the presence of the pseudogap and d superconducting phases (DSC) in a simple model for cuprates. The pseudogap phase is addressed within the framework of the ordered d ‐density wave (DDW). The above scenario is considered using a mean‐field calculation of the tight binding model which incorporates two layers – a CuO2 plane and a CuO chain per unit cell. The CuO chains become superconducting due to the proximity to the planes below the critical temperature. Moreover our model includes a momentum dependent chain‐plane coupling. We observe distinct behaviors for the penetration depth results along the three directions which is consistent with the anisotropy observed in the experimental results. The temperature dependence of λc is ex‐ actly the same as that of the recent experimental results as demonstrated for Tc = 18 K in the underdoped region. We observe a qualititave difference in the temperature dependence of λa and λb when compared to our previous studies. However the phase diagram due to the inclusion of the momentum dependence of the coupling suffers no significant variation. The main result of our work then is that a simple proximity DDW model in which the pairing interaction is localized to the planes and the planes are coupled to the chains through a momentum dependent term can account for many observed experimental properties. The inclusion of the pseudogap and also the value of the chain‐plane coupling modifies the general trend of our results when compared to the simple DSC model without the coupling. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Half‐metallic ferromagnetism in wurtzite SrC
Authors: Zhang Chang‐wen , Yan Shi‐shen , Li Hua 
Published: December 2007

AbstractThe first‐principles full potential linearized augmented plane‐wave method within density‐functional theory is used to investigate electronic structure and magnetism of wurtzite (WZ) crystal structure SrC. It is shown that the WZ SrC is a true half‐metallic ferromagnet with a magnetic moment of 2μB per formula unit. The large HM gaps (0.72 eV) and robustness of half‐metallicity with respect to the lattice change make it possible candidate grown epitaxially on appropriate substrates in the form of films thick enough, and therefore should be useful in spintronics and other related applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and electronic properties of few‐layer graphenes from first‐principles
Authors: Huang J.‐R. , Lin J.‐Y. , Chen B.‐H. , Tsai M.‐H. 
Published: December 2007

AbstractThe first‐principles calculation method has been used to obtain structural and electronic properties of few‐layer graphenes (FLG's) with and without a cross‐film external electric potential, Vext. It is found that the AB stacking is more favorable than the AA stacking and the calculated layer spacing for the two‐layer AB stacked FLG is only 2.725 Å, which is substantially reduced from that of the bulk graphite of 3.257 Å. The two‐layer AB stacked FLG is found to exhibit a semi‐metal–semiconductor transition under Vext qualitatively in agreement with previous studies. However, the energy gap, Eg, is not limited at 0.3 eV as obtained in previous first‐principles calculation due to the reduced interlayer spacing. The threshold of the semi‐metal–semiconductor transition is 0.04 Volts. Vext also induces Eg's in 3‐ and 4‐layer AB stacked FLG's. However, in these FLG's the induced Eg's are small within 0.1 eV. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural, electronic and optical properties of II–IV–N2 compounds (II = Be, Zn; IV = Si, Ge)
Authors: Shaposhnikov V. L. , Krivosheeva A. V. , Arnaud D'Avitaya F. , Lazzari J.‐L. , Borisenko V. E. 
Published: December 2007

AbstractA detailed study of structural, electronic and optical properties of II–IV–N2 ternary compounds (II = Be, Zn; IV = Si, Ge) has been performed by means of ab initio density functional theory calculations. The germanium containing compounds were found to be direct‐gap semiconductors with gaps of 3.37 eV and 1.67 eV for BeGeN2 and ZnGeN2, respectively, with oscillator strength of direct transition comparable to GaN. Two other silicon containing compounds are characterized by indirect gaps of 5.19 (3.32) eV for BeSiN2 (ZnSiN2). Crystal structure being orthorhombic and lattice parameters for BeSiN2 and ZnSiN2 are in good agreement with the available experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Why are spin wave excitations all important in nanoscale magnetism?
Authors: Baberschke Klaus 
Published: December 2007

AbstractFor a proper interpretation of magnetic phenomena in low dimensional magnets, higher order spin wave excitations are more important than in bulk magnetism. Three different types of experiments will be discussed: (i) In a so‐called trilayer, two ferromagnetic films are coupled via a nonmagnetic spacer: FM1/ NM/FM2. The individual Curie temperatures can be shif‐ ted by 50 K or 100 K, just by tuning the NM thickness. This is impossible in 3D. (ii) Spin‐wave excitations are the major route to understanding the T‐dependence of the interlayer exchange coupling (IEC). (iii) The standard Gilbert damping is insufficient to describe the spin dynamics in nanomagnets. Magnon–magnon scattering, a reversible process in the magnetic subsystem, must first be disentangled in the spin dynamics, before determining the dissipative relaxation into the thermal bath. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Grain size reduction of CoCrPt–SiO2 media by oxidation of RuCr intermediate layer grain boundary
Authors: Park Sang Hwan , Kim Seon Ok , Oh Hoon Sang , Choa Sung Hoon , Lee Taek Dong 
Published: December 2007

AbstractThe grain size reduction mechanism of CoCrPt‐SiO2 perpendicular magnetic recording media by oxygen reactive sputtering of RuCr intermediate layer has been investigated as a function of oxygen content in the Ar sputtering gas. The media stack was Ta/Ru/RuCr/CoCrPt‐SiO2. It was found that, by the oxygen addition, Cr and Ru oxides were formed at grain boundaries of the RuCr layer and this was the reason of the intermediate layer grain size reduction, which induced the reduction of the recording layer grain size. C‐axis alignment of RuCr (0002) plane, however, was degraded as the oxygen gas ratio increased. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hydrogenation‐assisted crystallisation of amorphous Nd‐Fe‐B material
Authors: Kwon H. W. , Jeong I. C. 
Published: December 2007

AbstractCrystallisation of the Nd‐Fe‐B amorphous material assisted by a hydrogenation was investigated. The Nd‐Fe‐B amorphous material was prepared by mechanical milling of the Nd15Fe77B88 alloy ingot. The amorphous material was reacted with hydrogen gas to cause crystallisation. The hydrogenation facilitated the crystallisation of the amorphous Nd15Fe77B8 alloy, and the crystallisation was completed at the temperatures much lower than the ordinary thermal crystallisation temperature. The huge heat evolved from the hydrogenation assisted the crystallisation of the amorphous. The Nd15Fe77B8 material crystallised from the amorphous by the hydrogenation consisted of a mixture of NdHx, Fe and Nd1+xFe4B4 phases. The desorption of hydrogen from the mixture under vacuum at an elevated temperature led to a combination of Nd, Fe and Nd1+xFe4B4 phases into the Nd2Fe14B phase. The hydrogenation‐assisting crystallised material showed much higher coercivity after the desorption and combination with respect to the material thermally annealed without hydrogenation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Giant Faraday rotation in Cd1–xMnx Te (0 < x < 0.82) crystals
Authors: Hwang Younghun , Chung Soo‐seong , Um Youngho 
Published: December 2007

AbstractWe investigated the magneto‐optical properties of diluted magnetic semiconductors Cd1–x Mnx Te crystals grown using a vertical Bridgman method. This material crystallizes in the zinc‐blende structure for values of x < 0.82. The band‐gap energy was depended on Mn mole fraction x linearly and increased with decreasing temperature. The increase of the energy gap with increasing x may be due to a decrease in the lattice constant. Faraday rotation as a function of photon energy with various Mn compositions for CdMnTe in the temperature range of 10–300 K has been measured. The Faraday rotation was increased as the photon energy increased near to that of the fundamental band gap. Verdet constant becomes larger since the effect of the sp ‐d exchange interaction is enhanced as the temperature is lowered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)