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Full-Text Articles in Physics

Rewriting Magnetic Phase Change Memory By Laser Heating, John Timmerwilke, Sy-Hwang Liou, Shu Fan Cheng, Alan S. Edelstein Jan 2016

Rewriting Magnetic Phase Change Memory By Laser Heating, John Timmerwilke, Sy-Hwang Liou, Shu Fan Cheng, Alan S. Edelstein

Si-Hwang Liou Publications

Magnetic phase change memory (MAG PCM) consists of bits with different magnetic permeability values. The bits are read by measuring their effect on a magnetic probe field. Previously low permeability crystalline bits had been written in high permeability amorphous films of Metglas via laser heating. Here data is presented showing that by applying short laser pulses with the appropriate power to previously crystallized regions they can first be vitrified and then again crystallized. Thus, MAG PCM is rewriteable. Technical issues in processing the bits are discussed and results on thermal modeling are presented.


Positive Exchange Bias In Epitaxial Permalloy/Mgo Integrated With Si (100), S. S. Rao, J. T. Prater, Fan Wu, S. Nori, D. Kumar, Lanping Yue, Sy_Hwang Liou, Jagdish Narayan Jan 2014

Positive Exchange Bias In Epitaxial Permalloy/Mgo Integrated With Si (100), S. S. Rao, J. T. Prater, Fan Wu, S. Nori, D. Kumar, Lanping Yue, Sy_Hwang Liou, Jagdish Narayan

Si-Hwang Liou Publications

In magnetic random access memory (MRAM) devices, soft magnetic thin film elements such as permalloy (Py) are used as unit cells of information. The epitaxial integration of these elements with the technologically important substrate Si (100) and a thorough understanding of their magnetic properties are critical for CMOS-based magnetic devices. We report on the epitaxial growth of Ni82.5Fe17.5 (permalloy, Py) on Si (100) using a TiN/MgO buffer layer. Initial stages of growth are characterized by the formation of discrete islands that gradually merge into a continuous film as deposition times are extended. Interestingly, we ...


Magnetic Micro-Structural Uniformity Of Die-Upset Nd-Fe-B Magnets, Yikun Fang, Xiaolu Yin, Rui Zhao, Shah R. Valloppilly, Wei Li, Minggang Zhu, Sy-Hwang Liou Jan 2012

Magnetic Micro-Structural Uniformity Of Die-Upset Nd-Fe-B Magnets, Yikun Fang, Xiaolu Yin, Rui Zhao, Shah R. Valloppilly, Wei Li, Minggang Zhu, Sy-Hwang Liou

Si-Hwang Liou Publications

Die-upset Nd13.62Fe75.70Co4.45B5.76Ga0.47 magnets have been prepared with height reduction (h) in the range of 60 to 88%. The energy product as high as 50.4 MGOe was obtained in the sample with h~70%. The magnetic domains of the samples are revealed by using magnetic force microscopy (MFM). The average domain widths of the die-upset samples with surface normal parallel (//) and perpendicular (\) to the loading direction are in the range of w//: 0.4-0.6lm; w\: 0.9-3.8 μm, respectively. These interaction domains are formed due ...


Picotesla Magnetic Sensors For Low-Frequency Applications, Sy-Hwang Liou, Xiaolu Yin, Stephen Russek, Ranko Heindl, F. C. S. Da Silva, J. Moreland, David P. Pappas, L. Yuan, J. Shen Oct 2011

Picotesla Magnetic Sensors For Low-Frequency Applications, Sy-Hwang Liou, Xiaolu Yin, Stephen Russek, Ranko Heindl, F. C. S. Da Silva, J. Moreland, David P. Pappas, L. Yuan, J. Shen

Si-Hwang Liou Publications

We demonstrate a simple low-power, magnetic sensor system suitable for high-sensitivity magnetic-field mapping, based on solid-state magnetic tunnel junction devices with minimum detectable fields in a 100 pT range at room temperature. In this paper, we discuss a method that uses multilayer thin films to improve the performance of the soft ferromagnetic layer in magnetoresistive sensor applications, by reducing the coercivity and/or improving the reversibility.We have used it in the design of our new magnetic sensor. This sensor has a sensitivity as high as 750%/mT. The magnetic sensor only dissipates 1 mW of power while operating under ...


Dependence Of Noise In Magnetic Tunnel Junction Sensors On Annealing Field And Temperature, Sy-Hwang Liou, Rui Zhang, Stephen Russek, L. Yuan, Sean T. Halloran, David P. Pappas Mar 2008

Dependence Of Noise In Magnetic Tunnel Junction Sensors On Annealing Field And Temperature, Sy-Hwang Liou, Rui Zhang, Stephen Russek, L. Yuan, Sean T. Halloran, David P. Pappas

Si-Hwang Liou Publications

The minimum detectable field of magnetoresistive sensors is limited by their intrinsic noise. Magnetization fluctuations are one of the crucial noise sources and are related to the magnetization alignment at the antiferromagnetic-ferromagnetic interface. In this study, we investigated the low frequency noise of magnetic tunnel junctions (MTJs) annealed in the temperature range from 265 to 305 °C and magnetic fields up to 7 T, either in helium or hydrogen environments. Our results indicate that the magnetic fluctuators in these MTJs changed their frequency based on annealing field and temperature. The noise of the MTJs at low frequency can be reduced ...


Domain Overlap In Antiferromagnetically Coupled [Co/Pt]/Nio/ [Co/Pt] Multilayers, Andrew Baruth, Lu Yuan, John D. Burton, Karolina Janicka, Evgeny Y. Tsymbal, Sy_Hwang Liou, Shireen Adenwalla Nov 2006

Domain Overlap In Antiferromagnetically Coupled [Co/Pt]/Nio/ [Co/Pt] Multilayers, Andrew Baruth, Lu Yuan, John D. Burton, Karolina Janicka, Evgeny Y. Tsymbal, Sy_Hwang Liou, Shireen Adenwalla

Si-Hwang Liou Publications

Antiferromagnetically coupled magnetic thin films with perpendicular anisotropy exhibit domain overlap regions originating from magnetostatic stray fields localized in the vicinity of the domain walls. Using high resolution magnetic force microscopy, the authors investigate these overlap regions in [Co/Pt] /NiO/ [Co/Pt] multilayers with various strengths of the interlayer exchange coupling. They develop a simple model that provides a quantitative explanation of the formation of these regions and the relationship between the domain overlap width and the coupling strength. Their results are important for application of magnetic layered structures with perpendicular anisotropy in advanced magnetoresistive devices.


Sy-Hwang Liou Publications 1982–2006 Sep 2006

Sy-Hwang Liou Publications 1982–2006

Si-Hwang Liou Publications

Includes 204 articles and chapters, plus 2 patents. Current as of spring 2006.


Direct Synthesis Of Single-Walled Carbon Nanotubes Bridging Metal Electrodes By Laser-Assisted Chemical Vapor Deposition, J. Shi, Yongfeng Lu, K.J. Yi, Yushun Lin, Sy_Hwang Liou, J.B. Hou, X.W. Wang Aug 2006

Direct Synthesis Of Single-Walled Carbon Nanotubes Bridging Metal Electrodes By Laser-Assisted Chemical Vapor Deposition, J. Shi, Yongfeng Lu, K.J. Yi, Yushun Lin, Sy_Hwang Liou, J.B. Hou, X.W. Wang

Si-Hwang Liou Publications

Direct synthesis of single-walled carbon nanotubes (SWNTs) bridging prepatterned Mo electrodes has been achieved using laser-assisted chemical vapor deposition (LCVD). The synthesized SWNTs are found predominantly semiconducting. By controlling the spot size of the focused laser beam, synthesis of SWNTs can be achieved in a localized manner, which is governed by the thermal and optical properties of materials as well as the laser parameters. The synthesis process is fast and can be achieved in both far- and near-infrared laser wavelength regions. LCVD method provides a potential approach to in situ remove SWNTs with specific chiralities during the growth. © 2006 American ...


Origin Of The Interlayer Exchange Coupling In [Co/Pt]/Nio/ [Co/Pt] Multilayers Studied With Xas, Xmcd, And Micromagnetic Modeling, Andrew Baruth, D.J. Keavney, John D. Burton, Karolina Janicka, Evgeny Y. Tsymbal, Lu Yuan, Sy_Hwang Liou, Shireen Adenwalla Aug 2006

Origin Of The Interlayer Exchange Coupling In [Co/Pt]/Nio/ [Co/Pt] Multilayers Studied With Xas, Xmcd, And Micromagnetic Modeling, Andrew Baruth, D.J. Keavney, John D. Burton, Karolina Janicka, Evgeny Y. Tsymbal, Lu Yuan, Sy_Hwang Liou, Shireen Adenwalla

Si-Hwang Liou Publications

The origin of the oscillatory interlayer exchange coupling in [Co/Pt] /NiO/ [Co/Pt] multilayers is investigated using advanced microscopy and spectroscopy techniques and micromagnetic modeling. X-ray magnetic circular dichroism (XMCD) measurements show the presence of the canting of Ni spins in the NiO film being greater for antiferromagnetically coupled multilayers than for ferromagnetically coupled ones. This behavior is consistent with the model, which assumes a different sign of the exchange coupling at the two interfaces and the antiferromagnetic layer-by-layer coupling in the NiO film. An unexpectedly short attenuation length of 4 Å for secondary electrons in NiO is measured ...


Perturbation Of Magnetostatic Modes Observed By Ferromagnetic Resonance Force Microscopy, R. Urban, A. Putilin, P.E. Wigen, Sy_Hwang Liou, M.C. Cross, P.C. Hammel, M.L. Roukes Jun 2006

Perturbation Of Magnetostatic Modes Observed By Ferromagnetic Resonance Force Microscopy, R. Urban, A. Putilin, P.E. Wigen, Sy_Hwang Liou, M.C. Cross, P.C. Hammel, M.L. Roukes

Si-Hwang Liou Publications

Magnetostatic modes of yttrium iron garnet (YIG) films are investigated by ferromagnetic resonance force microscopy. A thin-film “probe” magnet at the tip of a compliant cantilever introduces a local inhomogeneity in the internal field of the YIG sample. This influences the shape of the sample’s magnetostatic modes, thereby measurably perturbing the strength of the force coupled to the cantilever. We present a theoretical model that explains these observations; it shows that the tip-induced variation of the internal field creates either a local “potential barrier” or “potential well” for the magnetostatic waves. The data and model together indicate that local ...


Microcantilever Torque Magnetometery Study Of Patterned Magnetic Films, L. Yuan, Lei Gao, Ildar F. Sabiryanov, Sy-Hwang Liou, M. D. Chabot, D. H. Min, J. Moreland, B. Han May 2006

Microcantilever Torque Magnetometery Study Of Patterned Magnetic Films, L. Yuan, Lei Gao, Ildar F. Sabiryanov, Sy-Hwang Liou, M. D. Chabot, D. H. Min, J. Moreland, B. Han

Si-Hwang Liou Publications

The study of the small, defined magnetic structures has attracted much attention due to interest in both technology applications and fundamental research in micromagnetism. Microcantilever torque magnetometry (MTM) is a promising new experimental technique for measuring such small magnetic features [1]. One of the challenges of using this technique is to place the sample on the cantilever. In this work, we develop a new process for preparing patterned magnetic film on cantilever and show a primarily result of magnetic interactions in a paired magnetic bar measured by MTM. The process of patterning the magnetic film on the cantilever is following ...


Magnetic Force Microscopy Study Of Coptcro Perpendicular Media With Superparamagnetic And Permanent Magnet Tips, L. Yuan, Lei Gao, L. Nicholl, Sy-Hwang Liou, M. Zheng, E. N. Abarra, B. R. Acharya, G. Choe, S. S. Malhotra, B. Han May 2006

Magnetic Force Microscopy Study Of Coptcro Perpendicular Media With Superparamagnetic And Permanent Magnet Tips, L. Yuan, Lei Gao, L. Nicholl, Sy-Hwang Liou, M. Zheng, E. N. Abarra, B. R. Acharya, G. Choe, S. S. Malhotra, B. Han

Si-Hwang Liou Publications

Magnetic force microscopy (MFM) has been widely used in the study of magnetic recording media. It requires high resolution MFM tips as well as better understanding of the obtained magnetic images. In this study, we compared the images obtained by superparamagnetic and permanent MFM tips, that allows us to explain the issues related to the frequency double in some of domain images of the recording media. We also investigated the domain structures of high density recording bits (up to 1100 kfci) written on ac and dc-erased CoPtCrO perpendicular magnetic recording (PMR) media with permanent magnet MFM tips under ambient conditions ...


Structure Of Sc2O3 Films Epitaxially Grown On Α -Al2O3 (0001), A.R. Kortan, N. Kopylov, J. Kwo, M. Hong, C.P. Chen, J.P. Mannaerts, Sy_Hwang Liou Jan 2006

Structure Of Sc2O3 Films Epitaxially Grown On Α -Al2O3 (0001), A.R. Kortan, N. Kopylov, J. Kwo, M. Hong, C.P. Chen, J.P. Mannaerts, Sy_Hwang Liou

Si-Hwang Liou Publications

The crystal structure of scandium oxide films epitaxially grown on α -Al2O3 (0001) under an ultrahigh-vacuum is studied by single-crystal x-ray diffraction. The Sc2O3 film grows in bixbyite phase on the basal (0001) surface of the sapphire substrate with its (111) axis aligned parallel to the substrate normal. In-plane orientation of the film, however, exhibits two distinct growth directions that are defined by the two possible surface orientations of the stepped α -Al2O3 substrate. The atomic structure of the high-quality epitaxial film is fully relaxed and the film has unusual thickness ...


Magnetization Reversal Of Fe Films On Ag Submicrometer Pyramidal Islands, Chin-Chung Yu, Yeong-Der Yao, Sy_Hwang Liou Oct 2005

Magnetization Reversal Of Fe Films On Ag Submicrometer Pyramidal Islands, Chin-Chung Yu, Yeong-Der Yao, Sy_Hwang Liou

Si-Hwang Liou Publications

Ag submicrometer pyramidal islands with a (100) truncated top and four (111) sidewalls were successfully fabricated on Si(100) substrates at a deposition temperature of 500/spl deg/C. The magnetization reversal of 30 nm thick Fe films grown on Ag pyramidal islands was studied by magnetic force microscopy. The magnetization reversal of Fe films was first started at the sidewalls of pyramidal islands. Then, the formation and propagation of wall-like structures were observed under a higher external magnetic field, namely 95 Oe. The magnetic domain images indicated that the Fe films grown on the sidewalls of pyramidal islands and ...


Magnetic Properties And L10 Phase Formation Of Fept Films Prepared By High Current-Density Ion-Beam Irradiation And Rapid Thermal Annealing Methods, T. Yokota, M.L. Yan, Yinfan Xu, L. Gao, R. Zhang, Leighann Nicholl, Lu Yuan, Ralph Skomski, David J. Sellmyer, Sy_Hwang Liou, Chih-Huang Lai, Cheng-Han Yang, Sheng-Huang Huang May 2005

Magnetic Properties And L10 Phase Formation Of Fept Films Prepared By High Current-Density Ion-Beam Irradiation And Rapid Thermal Annealing Methods, T. Yokota, M.L. Yan, Yinfan Xu, L. Gao, R. Zhang, Leighann Nicholl, Lu Yuan, Ralph Skomski, David J. Sellmyer, Sy_Hwang Liou, Chih-Huang Lai, Cheng-Han Yang, Sheng-Huang Huang

Si-Hwang Liou Publications

We investigated magnetic properties and L10 phase formation of FePt films by rapid thermal annealing (RTA) and high current-density ion-beam irradiation. The sample prepared by RTA at 550 °C has (001) texture and strong magnetic perpendicular anisotropy with Hc equal to 6 kOe. The sample irradiated at 5.04 µA/cm2 has Hc equal to 10 kOe but has isotropic magnetic properties due to the (111) texture. The magnetic correlation length of the ion-irradiated sample was about twice as large as that of the RTA sample. This may be due to the inhomogeneity of ...


The Perpendicular Magnetic Anisotropy Of Copt/Au Multilayer Films, T. Yokota, Lei Gao, R. Zhang, Leighann Nicholl, M. L. Yan, David J. Sellmyer, Sy-Hwang Liou Feb 2005

The Perpendicular Magnetic Anisotropy Of Copt/Au Multilayer Films, T. Yokota, Lei Gao, R. Zhang, Leighann Nicholl, M. L. Yan, David J. Sellmyer, Sy-Hwang Liou

Si-Hwang Liou Publications

We have studied the magnetic properties of Au (2 nm)/Co50Pt50 (3 nm)/Au (2 nm) multilayer films prepared on amorphous Al2O3/Si and (0 0 1) MgO substrates. The as-deposited films on both substrates are magnetically soft with an FCC structure and exhibit a perpendicular anisotropy. After annealing at 500 °C, the sample on the Al2O3/Si substrate has become magnetically isotropic but the sample on the MgO substrate still has perpendicular anisotropy with FCT structure. This film deposited on the MgO substrate did not show a strong perpendicular anisotropy ...


A Study Of Magnetic Interactions Of Ni80Fe20 Arrays Using Ultrasensitive Microcantilever Torque Magnetometry, L. Gao, D.Q. Feng, Lu Yuan, T. Yokota, Renat F. Sabirianov, Sy_Hwang Liou, M.D. Chabot, D. Porpora, J. Moreland Jun 2004

A Study Of Magnetic Interactions Of Ni80Fe20 Arrays Using Ultrasensitive Microcantilever Torque Magnetometry, L. Gao, D.Q. Feng, Lu Yuan, T. Yokota, Renat F. Sabirianov, Sy_Hwang Liou, M.D. Chabot, D. Porpora, J. Moreland

Si-Hwang Liou Publications

We have successfully fabricated single and paired 300 nm×1.5 µm×32 nm Ni80Fe20 bars on a microcantilever using focused ion beam milling. Magnetic interactions of the paired bars were studied by using magnetic force microscopy, microcantilever torque magnetometry, and micromagnetic simulation. Our results clearly indicate that the magnetic switching behavior of the paired Ni80Fe20 bars is affected by magnetostatic interactions. The magnetic hysteresis curves for a sample with eight pairs of Ni80Fe20 bars consist of a series of stable switching states that are related to the domain wall motion ...


Effect Of Au Spacer Layer On L10 Phase Ordering Temperature Of Copt Thin Films, T. Yokota, L. Gao, Sy_Hwang Liou, M.L. Yan, David J. Sellmyer Jun 2004

Effect Of Au Spacer Layer On L10 Phase Ordering Temperature Of Copt Thin Films, T. Yokota, L. Gao, Sy_Hwang Liou, M.L. Yan, David J. Sellmyer

Si-Hwang Liou Publications

We have studied the effect of Au on the ordering temperature of CoPt films. The coercivity of the CoPt multilayer with 2 nm Au inserted is around 5 kOe after annealing at 400 °C. This ordering temperature is about 200 °C lower than that of a pure CoPt film. Crystallographical analysis using x-ray diffraction has also revealed that the lattice constant is drastically changed around the same temperature, which is related to the formation of the L10-ordered structure. Thus, the Au plays an important role in reducing the ordering temperature.


United States Patent: Application Of High Spin Polarization Materials In Two Terminal Non-Volatile Bistable Memory Devices, Bernard Doudin, Andrei Sokolov, Cheol-Soo Yang, Lu Yuan, Sy-Hwang Liou Dec 2003

United States Patent: Application Of High Spin Polarization Materials In Two Terminal Non-Volatile Bistable Memory Devices, Bernard Doudin, Andrei Sokolov, Cheol-Soo Yang, Lu Yuan, Sy-Hwang Liou

Si-Hwang Liou Publications

Disclosed are two terminal bistable memory cells having least two high-spin polarization magnetic material junctions which are separated from one another by electron trap site defect containing insulator. The two terminal bistable memory cells demonstrate stable, low current readable, hysteretic resistance states which are set by the flow of a relatively high, (eg. a milliamp or less), plus or minus polarity D.C. current therethrough, which resistance is monitored by lower magnitude A.C. or D.C. current flow therethrough. Preferred cells have at least one Cr02/Cr203/ CrO2 sequence but typically have multiple Cr0 ...


Fabrication Of Nonepitaxially Grown Double-Layered Fept:C/Feconi Thin Films For Perpendicular Recording, M.L. Yan, Xingzhong Li, L. Gao, Sy_Hwang Liou, David J. Sellmyer, R.J.M Van De Veerdonk, K.W. Wierman Oct 2003

Fabrication Of Nonepitaxially Grown Double-Layered Fept:C/Feconi Thin Films For Perpendicular Recording, M.L. Yan, Xingzhong Li, L. Gao, Sy_Hwang Liou, David J. Sellmyer, R.J.M Van De Veerdonk, K.W. Wierman

Si-Hwang Liou Publications

A noneptaxially grown double-layered thin-film medium of nanocompsite FePt:C with a FeCoNi soft underlayer for high-density perpendicular magnetic recording was fabricated and investigated. Square-shaped perpendicular loops with a remanance ratio nearly equal to one and a coercivity as large as 8.5 kOe were obtained for this ordered FePt:C double-layered medium. The formation of the ordered L10 phase is confirmed by electron diffraction experiments. Transmission electron microscope observations reveal that FePt grains with a uniform size less than 5 nm are embedded in the C matrix and appear to be well isolated. Our results show that nonepitaxially ...


Magnetotransport Properties Of Cro2 Films Down To Single-Grain Sizes, Lu Yuan, Y. Ovchenkov, Andrei Sokolov, C.-S. Yang, Bernard Doudin, Sy_Hwang Liou May 2003

Magnetotransport Properties Of Cro2 Films Down To Single-Grain Sizes, Lu Yuan, Y. Ovchenkov, Andrei Sokolov, C.-S. Yang, Bernard Doudin, Sy_Hwang Liou

Si-Hwang Liou Publications

The magnetotransport properties of CrO2 films down to single-grain sizes have been investigated. The magnetoresistance of highly grain oriented CrO2 (100) films, deposited onto TiO2 (100) substrates using a high pressure cell, has been measured in the temperature range of 1.5–300 K and in magnetic fields up to 6 T. The difference in the magnetoresistance at the low temperature of these samples is related to the value of the residual resistance ratio (RRR = R273 K/R4.2 K) of the samples. The negative magnetoresistance observed in some of these films is likely due ...


Recording Characteristics Of Perpendicular Magnetic Media With Cozrnb, Nifenb, And Exchange-Pinned Nifenb Soft Magnetic Underlayers, Min Zheng, Albert Chekanov, Geon Choe, Kenneth E. Johnson, Lan Gao, Sy_Hwang Liou May 2003

Recording Characteristics Of Perpendicular Magnetic Media With Cozrnb, Nifenb, And Exchange-Pinned Nifenb Soft Magnetic Underlayers, Min Zheng, Albert Chekanov, Geon Choe, Kenneth E. Johnson, Lan Gao, Sy_Hwang Liou

Si-Hwang Liou Publications

The recording performance of perpendicular media with amorphous CoZrNb, nanocrystalline NiFeNb, and exchange-pinned FeMn/NiFeNb soft magnetic underlayers (SULs) has been studied. A method has been proposed to quantify the spike noises from the SUL. We found that media with higher permeability NiFeNb SULs showed 4 db higher signal-to-noise ratio than media with lower permeability CoZrNb SULs. The exchange-pinned NiFeNb SUL suppresses spike noise and offers good recording performance. Furthermore, the recording frequency dependence of dynamic coercivity (Hc) was strongly affected by the use of different SULs. The increase in dynamic Hc with linear density is negligibly small ...


Magnetic Force Microscopy Observations Of The Magnetic Behavior In Co–C Nanodot Arrays, L. Gao, Sy_Hwang Liou, M. Zheng, Ralph Skomski, M. L. Yan, David J. Sellmyer, N.I. Polushkin May 2002

Magnetic Force Microscopy Observations Of The Magnetic Behavior In Co–C Nanodot Arrays, L. Gao, Sy_Hwang Liou, M. Zheng, Ralph Skomski, M. L. Yan, David J. Sellmyer, N.I. Polushkin

Si-Hwang Liou Publications

The nanomagnetic behavior of Co–C nanodot arrays was investigated by magnetic force microscopy (MFM) and an alternative gradient force magnetometer. The direction of the easy axis can be observed directly with MFM by comparing the saturated magnetization state and the remanent magnetization state. Interaction of the domain wall with local defects was observed by field dependent MFM measurements. Some types of defects that can pin domain wall movement were identified.


Magnetoresistance Study In Thin Zig Zag Nife Wires, J. L. Tsai, S.F. Lee, Y.D. Yao, C. Yu, Sy_Hwang Liou May 2002

Magnetoresistance Study In Thin Zig Zag Nife Wires, J. L. Tsai, S.F. Lee, Y.D. Yao, C. Yu, Sy_Hwang Liou

Si-Hwang Liou Publications

Thickness dependence on the domain wall resistivity of zig zag thin permalloy wires was studied from 10 to 300 K. The maximum domain wall resistivity was obtained in wire with 100-nm-film thickness. The multidomain state resistivity was 14.29 µΩ cm, while single-domain state resistivity was 14.36 µΩ cm at 10 K. The ratio of domain wall magnetoresistance was measured to be 0.034%, 0.112%, and 0.258%, and the magnetic field where the domain wall started to switch was measured as –70, –40, and +80 Oe for wires with thicknesses of 20, 40, and 100 nm, respectively ...


Magnetic Intergranular Interaction In Nanocomposite CoΧPt100-Χ:C Thin Films, Nathan D. Powers, M.L. Yan, L. Gao, Sy_Hwang Liou, David J. Sellmyer May 2002

Magnetic Intergranular Interaction In Nanocomposite CoΧPt100-Χ:C Thin Films, Nathan D. Powers, M.L. Yan, L. Gao, Sy_Hwang Liou, David J. Sellmyer

Si-Hwang Liou Publications

Magnetization reversal and intergranular interactions have been studied in composite CoχPt100-χ:C thin films using several magnetic characterization techniques. The intergranular interactions, as determined by ΔM curves, were strongly dependent on the ratio of Co and Pt concentration. For films with high Co content, the intergranular exchange coupling was predominant, while dipolar interactions were exhibited in the film with the equiatomic concentration of Co and Pt. Magnetic intergranular interaction was directly observed using magnetic force microscopy. There is a strong correlation between the value of the ΔM and magnetic correlation length obtained from the magnetic ...


Zero-Bias Anomaly In Cro2 Junctions, Andrei Sokolov, C.-S. Yang, Lu Yuan, Sy_Hwang Liou, Ruihua Cheng, H.-K. Jeong, T. Komesu, B. Xu, C.N. Borca, Peter A. Dowben, Bernard Doudin May 2002

Zero-Bias Anomaly In Cro2 Junctions, Andrei Sokolov, C.-S. Yang, Lu Yuan, Sy_Hwang Liou, Ruihua Cheng, H.-K. Jeong, T. Komesu, B. Xu, C.N. Borca, Peter A. Dowben, Bernard Doudin

Si-Hwang Liou Publications

CrO2 thin films, with crystallites of several microns size, provide the opportunity for the investigation of the intergrain tunneling between a few crystals separated by a 1-2 nm thick Cr2O3 film. A pronounced zero-bias anomaly of the conductance is found at low temperatures. Combined photoemission and inverse photoemission temperature-dependent studies confirm the occurrence of Coulomb blockade. For the strong-tunneling case (R2), the magnetoresistance decreases strongly with bias. For the weak-tunneling case (R>>RQ), the magnetoresistance decreases by a factor two with increasing bias, as predicted by a co-tunneling model.


Electronic-Structure Modifications Induced By Surface Segregation In La0.65Pb0.35Mno3 Thin Films, C.N. Borca, B. Xu, T. Komesu, H.-K. Jeong, M.T. Liu, Sy_Hwang Liou, Shane Stadler, Y. Idzerda, Peter A. Dowben Dec 2001

Electronic-Structure Modifications Induced By Surface Segregation In La0.65Pb0.35Mno3 Thin Films, C.N. Borca, B. Xu, T. Komesu, H.-K. Jeong, M.T. Liu, Sy_Hwang Liou, Shane Stadler, Y. Idzerda, Peter A. Dowben

Si-Hwang Liou Publications

Using spin-polarized inverse photoemission and X-ray absorption spectroscopy techniques, we show that the electronic structure of La0.65Pb0.35MnO3 thin films depends on the composition at the surface. With a gentle annealing procedure, the surface provides a maximum of 80% spin asymmetry at 0.5 eV above the Fermi level in spite of extensive Pb segregation. A heavily annealed (restructured) surface exhibits a reduced surface "ordering" temperature of 240 K (compared to the approximately 335 K bulk value) as well as a reduced spin asymmetry value of 40% at 0.5 eV above Fermi energy.


Magnetic Nanodot Arrays Produced By Direct Laser Interference Lithography, M. Zheng, M. Yu, Yi Liu, Ralph Skomski, Sy_Hwang Liou, David J. Sellmyer, V.N. Petryakov, Yu K. Verevkin, N.I. Polushkin, N. N. Salashchenko Oct 2001

Magnetic Nanodot Arrays Produced By Direct Laser Interference Lithography, M. Zheng, M. Yu, Yi Liu, Ralph Skomski, Sy_Hwang Liou, David J. Sellmyer, V.N. Petryakov, Yu K. Verevkin, N.I. Polushkin, N. N. Salashchenko

Si-Hwang Liou Publications

Periodic magnetic nanodot arrays have been produced on an area as large as 1 cm×1 cm by direct nanolithography using interferometric laser radiation. The dots are formed by the local annealing of sputtered amorphous Co–C films in regions where the laser intensity is highest. At room temperature the dots exhibit ferromagnetic order and are embedded in a paramagnetic matrix. The onset of room-temperature ferromagnetism is caused by nanoscale chemical and morphological changes during dot formation and reflects the phase separation of magnetic Co-rich clusters. The present single-step nanolithography is potentially an efficient method for fabrication of patterned magnetic ...


Ferromagnetic Co-C Nanodot Arrays Produced By Direct Interferometric Laser Annealing, M. Zheng, M. Yu, Yi Liu, Ralph Skomski, David J. Sellmyer, V.N. Petryakov, Yu. K. Verevkin, Nikolay Polushkin, N.N. Salashchenko Jul 2001

Ferromagnetic Co-C Nanodot Arrays Produced By Direct Interferometric Laser Annealing, M. Zheng, M. Yu, Yi Liu, Ralph Skomski, David J. Sellmyer, V.N. Petryakov, Yu. K. Verevkin, Nikolay Polushkin, N.N. Salashchenko

Si-Hwang Liou Publications

Magnetic properties of Co-C nanodot arrays produced by direct interferometric laser annealing are investigated by magnetic force microscopy (MFM) and magnetization measurements. The dots are formed by locally annealing sputtered amorphous Co-C films in regions where the laser intensity is highest. As-sputtered Co-C films do not exhibit ferromagnetic order at room temperature, but MFM shows that the dots become magnetic upon annealing, possibly due to the agglomeration or phase separation of Co-rich clusters. The dots are embedded in either a paramagnetic or weakly magnetic matrix. The magnetic properties of the generated pattern can be changed by varying the laser power ...


Magnetic Properties And Nanostructures Of Composite, M.L. Yan, Yi Liu, M.J. Yu, Sy_Hwang Liou, David J. Sellmyer Jul 2001

Magnetic Properties And Nanostructures Of Composite, M.L. Yan, Yi Liu, M.J. Yu, Sy_Hwang Liou, David J. Sellmyer

Si-Hwang Liou Publications

Nanocomposite CoχPt100100-χ :C thin films with χ = 57 and χ = 50 were prepared by magnetron sputtering. Structures and activation volumes were studied systematically in order to better understand the magnetic behavior.We found that activation volumes of these two samples were almost the same. However, physical grain sizes of these two samples were different. Magnetic grains in the sample with equiatomic Co and Pt composition were almost independently switched and magnetic grains in the sample with higher Co content were exchange coupled and switched together. The reduction of the physical grain size in the sample does ...