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Full-Text Articles in Physics
Magnetization Reversal Behavior In Cobalt Rare-Earth Thin Films, S.S. Malhotra, Z.S. Shan, D.C. Stafford, Sy_Hwang Liou, David J. Sellmyer
Magnetization Reversal Behavior In Cobalt Rare-Earth Thin Films, S.S. Malhotra, Z.S. Shan, D.C. Stafford, Sy_Hwang Liou, David J. Sellmyer
David Sellmyer Publications
Cobalt RareEarth (CoR, R = Pr,Sm) thin films on a Cr underlayer have shown promise as future ultra high density magnetic recording media. The activation volume or the magnetic switching volume (v*) is an important consideration for thermal stability and media noise in high density recording media and V* can also provide information about the magnetization reversal behavior in these films. The magnetic switching volume was estimated for the CoPr films with thicknesses from 28 to 639 nm with a Cr underlayer of 80 nm annealed at 500 0C. The measured switching volume ranges from 1.3 to 1.7x10-18 …
High Coercivity Smfesic Films Fabricated By Multilayer Sputtering, S.Y. Zhang, Z.S. Shan, Yi Liu, David J. Sellmyer
High Coercivity Smfesic Films Fabricated By Multilayer Sputtering, S.Y. Zhang, Z.S. Shan, Yi Liu, David J. Sellmyer
David Sellmyer Publications
SmFeSiC thin films have been obtained by sputtering SmFe/C(Si) multilayers with a Ta underlayer on Si substrates and subsequently annealing at 700° C. The coercivity of the SmF films strongly depends on the sputtering and annealing conditions. The influence of the thickness of the Ta underlayer, the thickness ratio of SmFe to C(Si), the argon pressure and heat treatment In- plane Coercivities up to 7.2 kOe and squareness of 0.94 were obtained.
Lorentz Microscopy Observation Of Magnetic Grains In Co-Sm // Cr Films, Yi Liu, Z.S. Shan, David J. Sellmyer
Lorentz Microscopy Observation Of Magnetic Grains In Co-Sm // Cr Films, Yi Liu, Z.S. Shan, David J. Sellmyer
David Sellmyer Publications
This paper presents our recent Lorentz microscopy study of magnetic domain structure and its relation to the nanostructure of Co-Sm films. The magnetic domains were imaged by Foucault Lorentz mode and the corresponding nanostructure was revealed by bright field and high resolution images. The nanostructure is composed of clusters of 20 nm grown on Cr grains. Each cluster is formed by the amorphous matrix and about 5 nm crystallites distributed in the matrix. It is found that each cluster forms a magnetic grain. Such magnetic grains show uniform contrast near the magnetic domain wall, and correspond to the switching volume …
Magnetic Hardening Of Melt-Spun Nanocomposite Nd2Fe14B/Fe Magnets, I. Panagiotopoulos, L. Withanawasam, A.S. Murthy, George C. Hadjipanayis, E.W. Singleton, David J. Sellmyer
Magnetic Hardening Of Melt-Spun Nanocomposite Nd2Fe14B/Fe Magnets, I. Panagiotopoulos, L. Withanawasam, A.S. Murthy, George C. Hadjipanayis, E.W. Singleton, David J. Sellmyer
David Sellmyer Publications
Coercivity optimization studies were done on melt-spun nanocomposite Nd4R2Fe87-xNbTxB6 (R=Nd,Y,Dy; T=Ag,Cu) isotropic ribbon samples. The maximum attainable coercivities, after adjusting the annealing time, were found to be very sensitive to the annealing temperatures. The optimum magnetic properties [Hc=3.9 kOe, (BH) max=10 MGOe] were obtained by annealing at 750–775 °C for a few minutes. Optimization by flash annealing gave similar results. Microstructural studies show that the grain size is greater than the theoretically predicted grain size for optimum coupling between the hard and the soft phase. With the …
Magnetic Viscosity And Switching Volumes Of Annealed Fe/Pt Multilayers, C.P. Luo, Z.S. Shan, David J. Sellmyer
Magnetic Viscosity And Switching Volumes Of Annealed Fe/Pt Multilayers, C.P. Luo, Z.S. Shan, David J. Sellmyer
David Sellmyer Publications
Magnetic viscosity and the phenomenon of the sweep-rate dependence of the coercivity are important for the characterization of magnetic recording media. The activation volume of magnetization reversal or switching volume is directly related to medium noise. The magnetic viscosity behavior of annealed Fe/Pt multilayers was studied and the switching volumes were obtained by both measurements of the sweep-rate dependence of coercivity and time dependence of magnetization. It is found that samples with larger coercivities have smaller switching volumes, and an estimate of the magnetic grain diameter is about 9 nm. The coercivity mechanisms are also discussed.
Mössbauer Study Of Permanent-Magnet R2Fe17-XMXCY Compounds, I. A. Al-Omari, E.W. Singleton, Y. Zheng, George C. Hadjipanayis, David J. Sellmyer
Mössbauer Study Of Permanent-Magnet R2Fe17-XMXCY Compounds, I. A. Al-Omari, E.W. Singleton, Y. Zheng, George C. Hadjipanayis, David J. Sellmyer
David Sellmyer Publications
We report Fe57 Mössbauer spectroscopy studies of the effect of carbon doping on the magnetic properties of the Fe sites of R2Fe17-xMxCy, and of the presence of multiple phases in these systems. In this study two systems, Sm2Fe14Al3Cy, where y=0, 1.0, 2.0, and 3.0, and Nd2Fe14.54Si2.46Cy, where y=0, 0.432, and 2.544, were measured at room temperature and analyzed. The ternary compounds R2Fe17-xMxCy studied here have the …
Co-Sm (1̅100)[0001]//Cr (1̅21̅)[ 1̅01] Epitaxy And Its Effects On Magnetic Properties Of Co-Sm//Cr Films, Yi Liu, David J. Sellmyer, B. W. Robertson
Co-Sm (1̅100)[0001]//Cr (1̅21̅)[ 1̅01] Epitaxy And Its Effects On Magnetic Properties Of Co-Sm//Cr Films, Yi Liu, David J. Sellmyer, B. W. Robertson
David Sellmyer Publications
It is well known that the Cr underlayer plays a critical role in generating large in-plane coercivity in Co-based magnetic thin films. In this paper we report in detail the Co-Sm (1̅100)[0001]//Cr (1̅21̅)[ 1̅01] epitaxy revealed by high resolution electron microscopy. The lattice mismatch between Co-Sm (1̅100) and Cr (1̅21̅) is less than 2%, suggesting an energetically favorable configuration. The high anisotropy observed in Co-Sm films is discussed by this epitaxial relation.