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Articles 1 - 10 of 10
Full-Text Articles in Physics
The Effect Of Cu-Doping On The Magnetic And Transport Properties Of La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William B. Yelon, Paul Ernest Parris, William Joseph James
The Effect Of Cu-Doping On The Magnetic And Transport Properties Of La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William B. Yelon, Paul Ernest Parris, William Joseph James
Physics Faculty Research & Creative Works
The effects of Cu-doping on the structural, magnetic, and transport properties of La0.7Sr0.3Mn1xCuxO3 (0<=x<=0.20) have been studied using neutron diffraction, magnetization, and magnetoresistance (MR) measurements. All samples show the rhombohedral structure with the R[overline 3]c space-group from 10 K to room temperature (RT). Neutron diffraction data suggest that some of the Cu ions have a Cu3+ state in these compounds. The substitution of Mn by Cu affects the MnO bond length and Mn-O-Mn bond angle resulting from the minimization of the distortion of the MnO6 octahedron. Resistivity measurements show that a metal to insulator transition occurs for the x>=0.15 samples. The x=0.15 sample shows the highest MR([approximate]80%), which might result from the co-existence of Cu3-Cu2+ and the dilution effect of Cu-doping on the double exchange interaction
Magnetic And Mössbauer Studies On Oxygen Deficient Perovskite, La₀.₆Sr₀.₄Feo3-Δ, Jinbo Yang, William B. Yelon, William Joseph James, X.-D. Zhou, Yixiang Xie, Harlan U. Anderson, Zili Chu
Magnetic And Mössbauer Studies On Oxygen Deficient Perovskite, La₀.₆Sr₀.₄Feo3-Δ, Jinbo Yang, William B. Yelon, William Joseph James, X.-D. Zhou, Yixiang Xie, Harlan U. Anderson, Zili Chu
Physics Faculty Research & Creative Works
Samples of La0.6Sr0.4Fe3-δ with varying oxygen vacancy contents were prepared by heating them in different gas flows. Magnetization measurement showed that samples with low oxygen vacancies have a magnetic ordering temperature in the range of 300-325 K while those with 9%-12% oxygen vacancies have a magnetic ordering temperature of 800 K and higher. Mössbauer spectra at 300 K exhibit paramagnetic or weak magnetic characteristics for the N2, O2, and air-quenched samples, whereas an average hyperfine field of 52 T is found for the CO/CO2 reduced samples. The heat treatment in …
Effect Of Oxygen Vacancies On The Magnetic Structure Of The La₀.₆Sr₀.₄Feo3-Δ Perovskite: A Neutron Diffraction Study, Zili Chu, William B. Yelon, Jinbo Yang, William Joseph James, Harlan U. Anderson, Yixiang Xie, Satish K. Malik
Effect Of Oxygen Vacancies On The Magnetic Structure Of The La₀.₆Sr₀.₄Feo3-Δ Perovskite: A Neutron Diffraction Study, Zili Chu, William B. Yelon, Jinbo Yang, William Joseph James, Harlan U. Anderson, Yixiang Xie, Satish K. Malik
Physics Faculty Research & Creative Works
Magnetic interactions in perovskite compounds of the type La1-xSrxMO3-δ (M=3d transition such as Mn and Fe) are presumed to arise through a super exchange between 3d electrons of the magnetic ions via oxygen orbitals. The magnetic structure of La0.6Sr0.4FeO3-δ has been studied with neutron diffraction. Oxygen vacancies were created by annealing samples under various gases including N2, air and mixtures of CO/CO2. All La0.6Sr0.4FeO3-δ compounds maintain the rhombohedral structure (space group R3̄c). The air- or oxygen-annealed samples have almost no oxygen …
X-Ray Absorption, Neutron Diffraction, And Mössbauer Effect Studies Of Mnzn-Ferrite Processed Through High-Energy Ball Milling, D. J. Fatemi, V. G. Harris, Mingxing Chen, Satish K. Malik, William B. Yelon, Gary J. Long, Amitabh Mohan
X-Ray Absorption, Neutron Diffraction, And Mössbauer Effect Studies Of Mnzn-Ferrite Processed Through High-Energy Ball Milling, D. J. Fatemi, V. G. Harris, Mingxing Chen, Satish K. Malik, William B. Yelon, Gary J. Long, Amitabh Mohan
Physics Faculty Research & Creative Works
MnZn-ferrite has been prepared via high-energy ball milling of elemental oxides MnO, ZnO, and α-Fe2O3. Neutron diffraction measurements suggest a high density of vacancies in a spinel structure. The spinel phase appears to comprise 99.8 wt % of the material in the sample milled for 40 h, with the remainder attributable to unreacted α-Fe2O3. The x-ray absorption near-edge structure was analyzed to provide an understanding of the charge state of the constituent Fe ions. This analysis reveals about 2/3 of Fe cations to be trivalent, increasing to about 3/4 after a 5 …
Effects Of Sample Orientation On The Corrosion Of Zinc In Ammonium Sulfate And Sodium Hydroxide Solutions, D. Abayarathna, Edward Boyd Hale, Thomas J. O'Keefe, Y. M. Wang, D. Radovic
Effects Of Sample Orientation On The Corrosion Of Zinc In Ammonium Sulfate And Sodium Hydroxide Solutions, D. Abayarathna, Edward Boyd Hale, Thomas J. O'Keefe, Y. M. Wang, D. Radovic
Physics Faculty Research & Creative Works
The corrosion and electrochemical properties of three zinc single crystal surfaces with different orientations have been investigated. In near-neutral 1 M (NH4)2SO4, the corrosion rates on all three surfaces were found to be similar. However, the SEM morphologies of the corresponding corroded surfaces were markedly different from each other, but consistent with preferential attack of {1120} surfaces. In alkaline 0.5 N NaOH solution, the three sample orientations showed significantly different reactivities, with the (1120) surface exhibiting the highest reactivity and corrosion rate. Here, passivation ultimately occurred and the difference in the corrosion performance of …
Non-Linear Oscillation, Automodulation And Anelasticity, Tetsuro Suzuki, Manfred Wuttig
Non-Linear Oscillation, Automodulation And Anelasticity, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
The auto modulation observed in the course of internal friction is discussed as a special example of the universal nature of non-linear oscillations. Universal features of non-linear oscillations are the requirement of energy supply or negative damping and the period doubling route to chaos. The negative damping responsible for the auto modulation is described in terms of the soliton model for twinning deformation. © 1984 The Japan Society of Applied Physics.
Nonlinear Anelasticity Of Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Nonlinear Anelasticity Of Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
An approximate solution of the equation of motion of a nonlinear anelastic reed at or near resonance is presented. The steady state solution reproduces the well-known nonlinear resonances. The solution also predicts the existence of auto modulations, i.e., self-excited modulations of the amplitude and phase at constant power of excitation of the reed. Numerical examples of such auto modulations are presented for an antisymmetric deformation potential. Experimental studies of finite amplitude oscillations of a magnesium reed vibrating at 72 and 431 Hz at room temperature confirm the existence of auto modulations. The experimental results can be semi quantitatively described in …
Phaseautomodulation In Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Phaseautomodulation In Magnesium, Alexander Aning, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
No abstract provided.
Measurement Of The Wear Properties Of Metallic Solids With A Falex Lubricant Testing Machine, Edward Boyd Hale, Chun-Ping John Meng, Ronald A. Kohser
Measurement Of The Wear Properties Of Metallic Solids With A Falex Lubricant Testing Machine, Edward Boyd Hale, Chun-Ping John Meng, Ronald A. Kohser
Physics Faculty Research & Creative Works
A modified Falex Lubricant Testing Machine has been used to determine wear properties of metallic solids. In particular, wear mass loss, wear volume loss, wear rates, and other parameters have been determined for a basic steel, as heat treated and after ion implantation. Wear rate improvements of more than an order of magnitude were found in a nickel-chrome steel (SAE 3135) implanted with 2.5x1017 N+2/cm2. Wear tests were conducted with a cylinder-in-groove geometry in a mild lubricating oil with loads greater than 540 N, which corresponded to pressures which exceeded 108N/m2 …
Analogy Between Spinodal Decomposition And Martensitic Transformation, Tetsuro Suzuki, Manfred Wuttig
Analogy Between Spinodal Decomposition And Martensitic Transformation, Tetsuro Suzuki, Manfred Wuttig
Physics Faculty Research & Creative Works
The translation of the theory developed for the spinodal decomposition of a supercooled alloy to the language appropriate for the martensitic transformation is carried out. In the spinodal theory, the stability of the alloy with respect to the composition fluctuation is examined, while in the present theory the stability of the crystal with respect to the shear displacement fluctuation, the transverse phonon, is studied. The analogy to the spinodal theory requires the revival of the strain gradient energy term or the couple stress term, the presence of which has been a subject of controversies for a long time since Laval. …