PubMed Health⌕ Search

Biomedical subjects

W J M de Jonge

Publications and source records attributed to W J M de Jonge.

5 recordsLinked to original sources
PubMed2006

Stabilization of metastable expanded face-centered-tetragonal manganese.

The structural and magnetic properties of Mn prepared on single crystalline face-centered-tetragonal (fct) Co(001) were investigated. Mn grows coherently up to at least 50 monolayers (ML) and adopts a metastable expanded fct(001) phase [c/a = 1.055(5)]. This new fct-Mn phase was recently predicted theoretically by Hafner and Spisák. Studies of magnetic Mn/Co interface exchange interactions prove the room temperature antiferromagnetic state for thicknesses above 2.5 ML. The magnetic anisotropy of the thin Mn is high enough to induce a significant exchange anisotropy for Mn thicknesses as low as 6 ML. The potential of fct-Mn to become a novel model system for systematic studies on the exchange interactions at antiferromagnet/ferromagnet interfaces is discussed.

Journal Article↗
PubMed2005

Unifying ultrafast magnetization dynamics.

We present a microscopic model that successfully explains the ultrafast equilibration of magnetic order in ferromagnetic metals at a time scale tau(M) of only a few hundred femtoseconds after pulsed laser excitation. It is found that tau(M) can be directly related to the so-called Gilbert damping factor sigma that describes damping of GHz precessional motion of the magnetization vector. Independent of the spin-scattering mechanism, an appealingly simple equation relating the two key parameters via the Curie temperature T(C) is derived, tau(M) approximately c(0)h/k(B)T(C)sigma, with h and k(B) the Planck and Boltzmann constants, respectively, and the prefactor c(0) approximately 1/4). We argue that phonon-mediated spin-flip scattering may contribute significantly to the sub-ps response.

Journal Article↗
PubMed2004

Monolayer resolved oscillating hyperfine fields in epitaxial face-centered-tetragonal Co(001) films.

Ultrahigh-quality thin fct-Co films grown on Cu(001) have been investigated by 59Co nuclear magnetic resonance. The influence of the spin-dependent electron scattering at the interfaces is observed for at least four Co atomic layers from the interface with monolayer resolution. An oscillatory effect on the Co hyperfine field with a period of several monolayers is measured, corresponding to the oscillating conduction electron polarization. The observation is exclusively possible in this system due to its very narrow resonance lines, corresponding to a virtually perfect Co structure.

Journal Article↗
PubMed2002

Band structure and density of States effects in co-based magnetic tunnel junctions.

Utilizing Co/Al(2)O(3)/Co magnetic tunnel junctions with Co electrodes of different crystalline phases, a clear relationship between electrode crystal structure and junction transport properties is presented. For junctions with one fcc(111) textured and one polycrystalline (polyphase and polydirectional) Co electrode, a strong asymmetry is observed in the magnetotransport properties, while when both electrodes are polycrystalline the magnetotransport is essentially symmetric. These observations are successfully explained within a model based on ballistic tunneling between the calculated band structures (density of states) of fcc-Co and hcp-Co.

Journal Article↗