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Series

1990

David Sellmyer Publications

Articles 1 - 9 of 9

Full-Text Articles in Physics

Magnetism Of Rare-Earth–Transition-Metal Nanoscale Multilayers. I. Experiments On Dy/Co, Dy/Fe, And Tb/Fe, Z.S. Shan, David J. Sellmyer Dec 1990

Magnetism Of Rare-Earth–Transition-Metal Nanoscale Multilayers. I. Experiments On Dy/Co, Dy/Fe, And Tb/Fe, Z.S. Shan, David J. Sellmyer

David Sellmyer Publications

Experimental investigations of magnetic and structural properties for rare-earth–transition-metal (RE-TM) compositionally modulated films (CMF) are presented in this paper. In particular, ARE/BTM including ARE=Dy and Tb and BTM=Fe, Co, and Ni, are studied. The layer thickness and temperature dependence of magnetic properties, which can be interpreted in terms of the antiferromagnetic coupling of RE and TM moments and their atomic distributions, are reported. These ARE/BTM CMF with nanoscale layer thicknesses exhibit perpendicular magnetic anisotropy (PMA) and the range of the layer thickness required for PMA is determined. The origin ...


Magnetism Of Rare-Earth–Transition-Metal Nanoscale Multilayers. Ii. Theoretical Analysis Of Magnetization And Perpendicular Magnetic Anisotropy, Z.S. Shan, David J. Sellmyer, Sitaram Jaswal, Y.J. Wang, J.X. Shen Dec 1990

Magnetism Of Rare-Earth–Transition-Metal Nanoscale Multilayers. Ii. Theoretical Analysis Of Magnetization And Perpendicular Magnetic Anisotropy, Z.S. Shan, David J. Sellmyer, Sitaram Jaswal, Y.J. Wang, J.X. Shen

David Sellmyer Publications

Systematic studies of rare-earth–transition-metal amorphous compositionally modulated films (CMF) permit the development of a detailed model for understanding the magnetization and perpendicular magnetic anisotropy and their distributions along the film normal. It is shown that the single-ion anisotropy of rare-earth ions with orbital angular momentum is the major contributor to the perpendicular anisotropy for this class of CMF. The calculated results agree well with the experimental data for Dy/Co and Tb/Fe CMF when the individual layer thicknesses are small enough (<10 Å); these films have structures which can be characterized as compositionally modulated amorphous alloys.


Kerr Effect Of Two-Medium Layered Systems, Liang-Yao Chen, William A. Mcgahan, Z.S. Shan, David J. Sellmyer, John A. Woollam Jun 1990

Kerr Effect Of Two-Medium Layered Systems, Liang-Yao Chen, William A. Mcgahan, Z.S. Shan, David J. Sellmyer, John A. Woollam

David Sellmyer Publications

Detailed and practical expressions are given for the magneto-optical Kerr effect (MOKE) for various configurations of two media. One is a magneto-optic (MO) one, and the other is a nonmagnetic (NM) medium. For a system of two thick media with a single interface, with a first-order approximation in MOKE term Q, the Kerr function is determined by the product of a MOKE term Q and an optical term η. A second type of system includes a thin MO (or NM) layer deposited on a thick NM (or MO) substrate. For a MO/(NM-substrate) configuration, the Kerr function is related to ...


Enhancement Of Magneto-Optical Kerr Effects, Liang-Yao Chen, William A. Mcgahan, Z.S. Shan, David J. Sellmyer, John A. Woollam May 1990

Enhancement Of Magneto-Optical Kerr Effects, Liang-Yao Chen, William A. Mcgahan, Z.S. Shan, David J. Sellmyer, John A. Woollam

David Sellmyer Publications

A general expression for the magneto-optical polar Kerr effect is given for a bilayered configuration in which the optical constants of the two media differ. The equation shows that a giant enhancement of the Kerr effect in magneto-optical/metallic bilayers can be expected if the dielectric constants of the two materials are low or are matched well to the other. An explicit equation is also given to calculate the spectral enhancement due to a dielectric overcoating on magnetic substrates. An example is given for SiO-coated Dy/Co compositionally modulated alloys, yielding a good comparison to the experimental results in both ...


Magnetic And Structural Properties Of Cocrta Films And Multilayers With Cr, David J. Sellmyer, D. Wang, J.A. Christner May 1990

Magnetic And Structural Properties Of Cocrta Films And Multilayers With Cr, David J. Sellmyer, D. Wang, J.A. Christner

David Sellmyer Publications

We report our studies of epitaxial growth of CoCrTa films on Cr underlayers and the properties of CoCrTa/Cr multilayers. The coercivity, Hc, strongly depends on Ta composition, sputtering conditions, and the thicknesses of the magnetic layer and Cr underlayer. An Hcvalue of 1300 Oe was obtained for a Ta composition of 2 at. %, a Cr underlayer thickness of 4000 Å, and a magnetic layer thickness of 400 Å. The x-ray data show that the high Hc occurs when crystallites of the Cr underlayer and CoCrTa layer are aligned with the Cr (200) and CoCrTa (110 ...


Magnetism And Anisotropy Of Tb/Fe Multilayers, Z.S. Shan, David J. Sellmyer May 1990

Magnetism And Anisotropy Of Tb/Fe Multilayers, Z.S. Shan, David J. Sellmyer

David Sellmyer Publications

Studies of the layer-thickness dependence of hysteresis loops for Tb/Fe compositionally modulated films (CMF) are reported. The characteristics of magnetic properties, such as magnetization and uniaxial anisotropy, which depend on the FE layer thickness, can be interpreted in terms of the compositional dependence of magnetic properties of the constituent subnetworks and the spatial distribution of the constituent atoms. The magnetic properties of Tb/Fe CMF are analyzed with a micromagnetic model, and the behavior of the anisotropy and constituent magnetization near the compensation point is discussed. Journal of Applied Physics is copyrighted by The American Institute of Physics.


Magnetic And Structural Properties Of High-Coercivity Pr2Fe14Bpr Cosputtered Films, K.D. Aylesworth, David J. Sellmyer, George C. Hadjipanayis May 1990

Magnetic And Structural Properties Of High-Coercivity Pr2Fe14Bpr Cosputtered Films, K.D. Aylesworth, David J. Sellmyer, George C. Hadjipanayis

David Sellmyer Publications

The results of structural and magnetic measurements on a series of films produced by cosputtering Pr21Fe72B7 and Pr are reported. The materials were deposited serially, 10–200 Å at a time, onto 700 °C Ta substrates attached to a computer-controlled stepping motor. The structure of the resulting films was examined by large- and small-angle x-ray diffraction, scanning electron microscopy, and by microprobe analysis. Magnetic measurements were made at temperatures from 4.2 to 300 K, in fields up to 80 kOe in a vibrating sample magnetometer. The films appear to consist of 1-µm grains of ...


Magnetic And Structural Studies In Sm-Fe-Ti Magnets, Y. Wang, George C. Hadjipanayis, A. Kim, N.C. Liu, David J. Sellmyer May 1990

Magnetic And Structural Studies In Sm-Fe-Ti Magnets, Y. Wang, George C. Hadjipanayis, A. Kim, N.C. Liu, David J. Sellmyer

David Sellmyer Publications

The effects of vanadium substitution on the magnetic properties of Sm-Fe-Ti-V melt-spun ribbons and the magnetic properties and microstructure of sintered Sm-Fe-Ti based magnets are reported. The highest coercivity, Hc =10.65 kOe, was obtained in a heat-treated melt-spun Sm8 Fe75.5 Ga0.5 Ti8 V8 alloy. This is the highest value of the coercivities reported in alloys with the ThMn12 -type structure. Bulk magnets were prepared by the usual powder metallurgy technique. However, their highest coercivity (~2 kOe) was much less than that of the corresponding ribbons. The low coercivity of sintered ...


Electronic Structure And Magnetic Properties Of Fe-Rich Ternary Compounds: Yfe10V2 And Yfe10Cr2, Sitaram Jaswal, Y.G. Ren, David J. Sellmyer May 1990

Electronic Structure And Magnetic Properties Of Fe-Rich Ternary Compounds: Yfe10V2 And Yfe10Cr2, Sitaram Jaswal, Y.G. Ren, David J. Sellmyer

David Sellmyer Publications

These compounds are prototypes of the Fe-rich ternary systems of ThMn12 structure which are of considerable current interest as permanent magnet materials. The electronic structure of YFe10V2 and YFe10Cr2 have been studied with photoemission and spin-polarized calculations. The Fe d states dominate the calculated density of states (DOS) near the Fermi energy and there is a good correspondence between the DOS and the experimental spectra. The calculated magnetization is in very good agreement with the experimental data. The calculations give a magnetic moment of ~1 µB at the V or Cr site ...