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- Abdul-Redah, T, et al.
(författare)
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Anomalous neutron Compton scattering in metallic hydrides: new experiments
- 2000
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Ingår i: PHYSICA B. - : ELSEVIER SCIENCE BV. - 0921-4526. ; 276, s. 824-825
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Tidskriftsartikel (refereegranskat)abstract
- The time-of-flight spectra of the neutron Compton scattering of solid palladium hydrides were measured at room temperature. This experiment, which was motivated by previous measurements on liquid H2O/D2O mixtures as mel as on niobium hydrides, showed anom
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- Blixt, Anna Maria, 1969-
(författare)
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Growth and Magnetic Properties of Fe- and FeNi-based Thin Films and Multilayers
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the growth and magnetic properties of thin films and multilayers. The samples were grown by magnetron sputtering, and characterized structurally mainly by x-ray diffraction and reflectivity. The magnetic characterization of the multilayers was done by magneto-optical Kerr technique, SQUID magnetometry and, in two samples, by neutron reflectometry.Arrays of small elements of polycrystalline permalloy (FeNi alloy with 19 wt% Fe) are of interest as a component in non-volatile magnetic random access memories (MRAM). Here the shape dependence of the domain structure in such elements was studied by magnetic force microscopy (MFM) and in thin ring magnets the 'onion' state could be seen for the first time. Also, by post-annealing in hydrogen atmosphere the number of domains decreased in each element due to enhanced relaxation and defect reduction.Furthermore, permalloy-based anisotropic magnetoresistance (AMR) in read heads are nowadays replaced by material combinations that have a giant magnetoresistance (GMR) effect. In this work Fe/V(001) and Fe0.82Ni0.18/V(001) superlattices, i.e. single-crystal-like multilayers, were investigated. These systems showed much smaller GMR effect compared to the Fe/Cr system. However, by introducing Ni into the Fe layers the magnetic anisotropy and the interlayer exchange coupling (IEC) decreased, thereby increasing the sensitivity, which is a key property for a magnetic sensor. The interface region showed a reduced magnetic moment, and the influence of the structural quality was modelled and investigated theoretically in the Fe0.82Ni0.18/V case. Also, in the Fe(2-3 ML)/V(x ML) superlattices (ML=monolayers) the transition temperature from long-range magnetic order to paramagnetic order oscillated with the V layer thickness (x) as a result of the oscillatory behaviour of the IEC.The introduction of hydrogen in the non-magnetic layers of, for example, Fe/V(001) superlattices is a way to tune the IEC strength. Here the tuning was used as a tool to study the magnetic order in a low-dimensional magnet. At the critical hydrogen concentration =0.022 the Fe layers in an Fe(2 ML)/V(13 ML) superlattice became decoupled. Then the system behaved as a two-dimensional Ising magnet with a finite ordering temperature of about 60 K.
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- Brucas, R., et al.
(författare)
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Magnetization and domain structure of bcc Fe81Ni19/Co (001) superlattices
- 2004
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 69:6, s. 064411/1-064411/11
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Tidskriftsartikel (refereegranskat)abstract
- Dense stripe domains were obsd. for a Fe81Ni19/Co superlattice grown on a MgO(100) single crystal substrate using dc magnetron sputtering. The stripe domain period exhibits irreversible changes with the magnetic field, as detd. by magnetic force microscopy. We present a simple theor. model for this system and calc. the magnetization and domain period as functions of the applied field by minimizing the total energy. For this purpose, an expression for the domain wall energy and wall width for arbitrary angles and one for the magnetostatic energy are derived. The model correctly predicts a decreasing domain period with the increasing applied field. At larger magnetic fields a transition to "chaotic" two-dimensional stripe patterns is obsd. and a qual. discussion of this phenomenon is given.
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