B. Koopmans
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Research Interests
B. Koopmans has a total of 37 co-authors. Here are the top co-authors by number of shared publications:
W. J. M. de Jonge
Department of Applied Physics and Center for NanoMaterials (cNM), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
4 shared publications- Jürgen T. Kohlhepp
Department of Applied Physics, Center for NanoMaterials (cNM) and COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
3 shared publications M. van Kampen
Department of Applied Physics and Center for NanoMaterials (cNM), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
3 shared publications- Bryce Sydney Richards
Institute of Microstructure Technology Karlsruhe Institute of Technology Eggenstein‐Leopoldshafen Germany
2 shared publications H. J. M. Swagten
Eindhoven University of Technology
2 shared publicationsM. Cardona
Max‐Planck‐Institut für Festkörperforschung, Heisenbergstraße 1, D‐70569 Stuttgart, Germany
2 shared publications
Latest Publications
- 7 March 2011
- Published by AIP Publishing in Applied Physics Letters
- Vol. 98 (10) , 102512
Tunable magnetic domain wall oscillator at an anisotropy boundary
We propose a magnetic domain wall (DW) oscillator scheme, in which a low dc current excites gigahertz angular precession of a DW at a fixed position. The scheme consists of a DW pinned at a magnetic anisotropy step in a perpendicularly magnetized nanostrip. The frequency is tuned by the current flowing through the strip. A perpendicular external field tunes the critical current density needed for precession, providing great experimental flexibility. We investigate this system using a simple one-dimensional model and full micromagnetic calculations. This oscillating nanomagnet is relatively easy to fabricate and could find application in future nanoscale microwave sources.
- 7 March 2011
- Published by AIP Publishing in Applied Physics Letters
- Vol. 98 (10) , 102512
Tunable magnetic domain wall oscillator at an anisotropy boundary
We propose a magnetic domain wall (DW) oscillator scheme, in which a low dc current excites gigahertz angular precession of a DW at a fixed position. The scheme consists of a DW pinned at a magnetic anisotropy step in a perpendicularly magnetized nanostrip. The frequency is tuned by the current flowing through the strip. A perpendicular external field tunes the critical current density needed for precession, providing great experimental flexibility. We investigate this system using a simple one-dimensional model and full micromagnetic calculations. This oscillating nanomagnet is relatively easy to fabricate and could find application in future nanoscale microwave sources.
- 1 March 2007
- Published by Elsevier in Journal of Magnetism and Magnetic Materials
- Vol. 310 (2) , 2012-2014
Tunneling spin polarization and annealing of Co72Fe20B8
- 1 March 2007
- Published by Elsevier in Journal of Magnetism and Magnetic Materials
- Vol. 310 (2) , 2012-2014
Tunneling spin polarization and annealing of Co72Fe20B8
- 8 January 2005
- Published by IOP Publishing in Journal of Physics: Condensed Matter
- Vol. 17 (2) , L27-L33
On the realization of artificial XY spin chains
- 8 January 2005
- Published by IOP Publishing in Journal of Physics: Condensed Matter
- Vol. 17 (2) , L27-L33
On the realization of artificial XY spin chains
- 14 September 2004
- Published by American Physical Society (APS) in Physical Review B
- Vol. 70 (11) , 115307
Excitonic enhancement of spin relaxation in diluted magnetic semiconductor quantum wells
We performed pump-probe magneto-optical Kerr spectroscopy to explore the role of excitonic effects on the electron and hole spin relaxation in -based quantum well structures. Particularly, important information is obtained from detailed interpretation of the temperature and wavelength dependence of the observed transient magneto-optics in specially engineered structures. In manganese-rich wells the electron spin relaxation is found to be strongly enhanced in the exciton due to the increased mass of the bound electron-hole pair, in agreement with earlier predictions. An even stronger enhancement of the relaxation time is found for the hole spin, which is explained by the additional mixing of heavy-hole and light-hole states in the bound state. In structures where Mn is confined to the barrier region, a different behavior is observed, indicative for a competition of various contributions.- 14 September 2004
- Published by American Physical Society (APS) in Physical Review B
- Vol. 70 (11) , 115307
Excitonic enhancement of spin relaxation in diluted magnetic semiconductor quantum wells
We performed pump-probe magneto-optical Kerr spectroscopy to explore the role of excitonic effects on the electron and hole spin relaxation in -based quantum well structures. Particularly, important information is obtained from detailed interpretation of the temperature and wavelength dependence of the observed transient magneto-optics in specially engineered structures. In manganese-rich wells the electron spin relaxation is found to be strongly enhanced in the exciton due to the increased mass of the bound electron-hole pair, in agreement with earlier predictions. An even stronger enhancement of the relaxation time is found for the hole spin, which is explained by the additional mixing of heavy-hole and light-hole states in the bound state. In structures where Mn is confined to the barrier region, a different behavior is observed, indicative for a competition of various contributions.- 28 May 2004
- Published by American Physical Society (APS) in Physical Review B
- Vol. 69 (17) , 172408
Role of the barrier in spin-dependent tunneling addressed with superconductor spectroscopy
To establish the role of the barrier material in spin-polarized tunneling, we directly measure the sign and magnitude of the tunneling spin polarization in Al/barrier/ferromagnet junctions with different barriers using the Zeeman-split superconducting density of states of the Al electrode. It is shown that clear Zeeman splitting is difficult to obtain with heavy metal oxide barriers, such as and due to a large spin-orbit scattering rate most likely induced by the heavy atoms at the Al/barrier interface. Junctions with MgO barriers, however, show clear Zeeman splitting and a tunneling spin polarization of with both Co and Fe as the top electrode, a number which significantly differs from found for our junctions. We claim that this barrier dependence originates from the electronic structure of the barrier/ferromagnet interface. The positive tunneling polarization is consistent with the presumption that due to the absence of d orbitals in the MgO barrier, tunneling is dominated by electrons with s character.- 28 May 2004
- Published by American Physical Society (APS) in Physical Review B
- Vol. 69 (17) , 172408
Role of the barrier in spin-dependent tunneling addressed with superconductor spectroscopy
To establish the role of the barrier material in spin-polarized tunneling, we directly measure the sign and magnitude of the tunneling spin polarization in Al/barrier/ferromagnet junctions with different barriers using the Zeeman-split superconducting density of states of the Al electrode. It is shown that clear Zeeman splitting is difficult to obtain with heavy metal oxide barriers, such as and due to a large spin-orbit scattering rate most likely induced by the heavy atoms at the Al/barrier interface. Junctions with MgO barriers, however, show clear Zeeman splitting and a tunneling spin polarization of with both Co and Fe as the top electrode, a number which significantly differs from found for our junctions. We claim that this barrier dependence originates from the electronic structure of the barrier/ferromagnet interface. The positive tunneling polarization is consistent with the presumption that due to the absence of d orbitals in the MgO barrier, tunneling is dominated by electrons with s character.- Top Cited Papers
- 24 July 2000
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 85 (4) , 844-847
Ultrafast Magneto-Optics in Nickel: Magnetism or Optics?
Several magnetic and optical processes contribute to the magneto-optical response of nickel thin films after excitation by a femtosecond laser pulse. We achieved a first complete identification by explicitly measuring the time-resolved Kerr ellipticity and rotation, as well as its temperature and magnetic field dependence in epitaxially grown (111) and (001) oriented Cu/Ni/Cu wedges. The first hundreds of femtoseconds the response is dominated by state filling effects. The true demagnetization takes approximately 0.5–1 ps. At the longer (sub-ns) time scales the spins are found to precess in their anisotropy field. Simple and transparent models are introduced to substantiate our interpretation.
- 24 July 2000
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 85 (4) , 844-847
Top Cited PapersUltrafast Magneto-Optics in Nickel: Magnetism or Optics?
Several magnetic and optical processes contribute to the magneto-optical response of nickel thin films after excitation by a femtosecond laser pulse. We achieved a first complete identification by explicitly measuring the time-resolved Kerr ellipticity and rotation, as well as its temperature and magnetic field dependence in epitaxially grown (111) and (001) oriented Cu/Ni/Cu wedges. The first hundreds of femtoseconds the response is dominated by state filling effects. The true demagnetization takes approximately 0.5–1 ps. At the longer (sub-ns) time scales the spins are found to precess in their anisotropy field. Simple and transparent models are introduced to substantiate our interpretation.
- 1 September 1999
- Published by Wiley in Physica Status Solidi (b)
- Vol. 215 (1) , 217-222
Electron and Hole Spin Dynamics in Magnetic Semiconductors
- 1 September 1999
- Published by Wiley in Physica Status Solidi (b)
- Vol. 215 (1) , 217-222
Electron and Hole Spin Dynamics in Magnetic Semiconductors
- 1 March 1999
- Published by Springer Nature in Applied Physics B
- Vol. 68 (3) , 525-530
Ultrafast spin dynamics in magnetic semiconductor quantum wells studied by magnetization modulation spectroscopy
- 1 March 1999
- Published by Springer Nature in Applied Physics B
- Vol. 68 (3) , 525-530
Ultrafast spin dynamics in magnetic semiconductor quantum wells studied by magnetization modulation spectroscopy
- 1 December 1998
- Published by Wiley in Physica Status Solidi (a)
- Vol. 170 (2) , 307-315
Microscopic Reflection Difference Spectroscopy on Semiconductor Nanostructures
- 1 December 1998
- Published by Wiley in Physica Status Solidi (a)
- Vol. 170 (2) , 307-315
Microscopic Reflection Difference Spectroscopy on Semiconductor Nanostructures
- 9 December 1996
- Published by AIP Publishing in Applied Physics Letters
- Vol. 69 (24) , 3719-3721
Growth of polycrystalline silicon on glass by selective laser-induced nucleation
Polycrystalline silicon on glass substrates was grown by a method based on the creation of nucleation sites using laser crystallization of amorphous silicon followed by thermal annealing at temperatures below 600 °C. Annealing induces the crystallization of the material around the seeds, eventually leading to coalescence of adjacent domains before spontaneous nucleation sets in. Micro-Raman spectroscopy shows that the seeds experience a tensile stress, which causes a radial birefringence in the surrounding amorphous silicon, detected by optical anisotropy measurements. We conjecture that this stress facilitates the crystallization of the material around the seed upon thermal annealing.
- 9 December 1996
- Published by AIP Publishing in Applied Physics Letters
- Vol. 69 (24) , 3719-3721
Growth of polycrystalline silicon on glass by selective laser-induced nucleation
Polycrystalline silicon on glass substrates was grown by a method based on the creation of nucleation sites using laser crystallization of amorphous silicon followed by thermal annealing at temperatures below 600 °C. Annealing induces the crystallization of the material around the seeds, eventually leading to coalescence of adjacent domains before spontaneous nucleation sets in. Micro-Raman spectroscopy shows that the seeds experience a tensile stress, which causes a radial birefringence in the surrounding amorphous silicon, detected by optical anisotropy measurements. We conjecture that this stress facilitates the crystallization of the material around the seed upon thermal annealing.