J. Kools - Academia.edu (original) (raw)
Papers by J. Kools
We demonstrate that 1/f noise is a sensitive probe for the micromagnetic aspects of the switching... more We demonstrate that 1/f noise is a sensitive probe for the micromagnetic aspects of the switching behavior in multilayered systems and spin valves, which show the Giant Magnetoresistance (GMR) effect. We studied patterned Ta/Ni_80Fe_20/Cu/Ni_80Fe_20/FeMn spin valves. Similar studies were performed on single Ni_80Fe_20 films, which show the anisotropic magnetoresistance (AMR) effect. First, we have found that the magnetoresistance effect itself
Philips Journal of Research, 1998
The technology of magnetoresistive element (MRE) fabrication and integration as well as some expe... more The technology of magnetoresistive element (MRE) fabrication and integration as well as some experimental results on the performance of anisotropic and giant magnetoresistive elements are discussed. Most emphasis is put on isolated MREs in specially designed test structures, although results on completed heads will also be discussed. Aspects such as output signal level, noise level, distortion and magnetic stability are
Applied Physics Letters - APPL PHYS LETT, 1994
We present magnetoresistance measurements on Ni80Fe20/Cu/Ni80Fe20/Fe50Mn50 spin valves with cross... more We present magnetoresistance measurements on Ni80Fe20/Cu/Ni80Fe20/Fe50Mn50 spin valves with crossed anisotropies: the easy magnetization direction of the unbiased Ni80Fe20 layer is perpendicular to the exchange biasing field which effectively works on the second Ni80Fe20 layer due to the interaction with the Fe50Mn50 layer. The hysteresis in the low-field magnetoresistance is less than 0.03 kA/m, which is ten times smaller than the hysteresis for similar materials with parallel anisotropies. The sensitivity (∂R/R∞)/∂H ranges from 8% to 18%/(kA/m), depending on the preparational method. To our knowledge this combination of very high sensitivity and very low coercivity has not been reported before.
Sensors and Actuators A: Physical, 1997
Journal of Magnetism and Magnetic Materials, 2000
Journal of Magnetism and Magnetic Materials, 1996
Journal of Applied Physics, 1992
The gas flow dynamics of laser ablation plumes is investigated experimentally and theoretically. ... more The gas flow dynamics of laser ablation plumes is investigated experimentally and theoretically. Experimentally, angular-resolved time-of-flight (ARTOF) measurements are performed on a model system (laser etching of copper in a chlorine environment). The TOF spectra ...
Journal of Applied Physics, 1997
Journal of Applied Physics, 1999
Abstract Spin valves are widely studied due to their application as magnetoresistive material in ... more Abstract Spin valves are widely studied due to their application as magnetoresistive material in magnetic recording heads and other magnetic field sensors. An important film property is the interlayer coupling field (called offset field H o or ferromagnetic coupling field H f). It ...
Journal of Applied Physics, 1997
Microfabricated magnetoresistive elements based on either the anisotropic or the giant magnetores... more Microfabricated magnetoresistive elements based on either the anisotropic or the giant magnetoresistance effect were tested for their frequency dependent resistance noise behavior at room temperature in a dc magnetic field, using a dc sense current. Thermal resistance noise was the dominant noise source above about 10 kHz. At low frequencies the resistance noise was found to be dominated by a
Journal of Applied Physics, 2010
IEEE Transactions on Magnetics, 2004
... Katrina Rook ... With a thinner NiFeCr a relatively thicker CoFe is needed in order to reach ... more ... Katrina Rook ... With a thinner NiFeCr a relatively thicker CoFe is needed in order to reach the high MR% boundary and vice-versa for a thinner CoFe. From the studies of the bilayer structure, the nonlinear Rs versus CoFe thickness has been observed. ...
IEEE Transactions on Magnetics, 1994
... In a yoke type thin film head the MRE property that mainly influences ?l is the product p,.t ... more ... In a yoke type thin film head the MRE property that mainly influences ?l is the product p,.t where t is the thickness of the active layer in the MRE and pr is its relative permeability [12]. ... "Analytical description of thin film yoke magneto-resistive heads", Philips J. Res. 36, pp. ...
IEEE Transactions on Magnetics, 1995
The conductivity of sputtered Ta/Cu/Ta and Ta/Ni80Fe 20/Ta thin films was measured for a film thi... more The conductivity of sputtered Ta/Cu/Ta and Ta/Ni80Fe 20/Ta thin films was measured for a film thickness ranging from 20 to 1500 Å. The measured data were analyzed using a semi-classical model for the electron transport, that includes grain boundary scattering, It was found that in these films grain boundaries are an important source of electron scattering, in Ni80Fe20 leading to
IEEE Transactions on Magnetics, 1995
Exchange-biased spin valve multilayers [ 11 are viable can-didates for application in thin film m... more Exchange-biased spin valve multilayers [ 11 are viable can-didates for application in thin film magnetic recording heads for hard disk [2] or tape applications [3], due to their sensitiv-ity to small magnetic fieids, in particular when permalloy (NigoFe20) is used as the' sensitive ...
We demonstrate that /f noise is a sensitive probe for the micromagnetic aspects of the switching ... more We demonstrate that /f noise is a sensitive probe for the micromagnetic aspects of the switching behavior in multilayered systems and spin valves, which show the Giant Magnetoresistance (GMR) effect. We studied patterned Ta/Ni_80Fe_20/Cu/Ni_80Fe_20/FeMn spin valves. Similar studies were performed on single Ni_80Fe_20 films, which show the anisotropic magnetoresistance (AMR) effect. First, we have found that the magnetoresistance effect itself transforms magnetic fluctuations into resistance fluctuations contributing to 1/f noise. This leads to an increased noise output as the sensitivity ( ~ dR/dH) of the spin valve is increased. Second, we have found a relation between the /f noise amplitude and micromagnetic effects (domain wall nucleation and pinning, ripple, etc.). These potential noise sources can be visualised by means of Kerr and Lorentz microscopy. Third, the role of interfacial scattering, the free and the exchange biased NiFe layer (in a crossed or parallel anisotropy configuration) and an incomplete exchange biasing is discussed. In order to seperate their contributions, we have performed noise experiments for various layer thickne! sses and compositions.
We demonstrate that 1/f noise is a sensitive probe for the micromagnetic aspects of the switching... more We demonstrate that 1/f noise is a sensitive probe for the micromagnetic aspects of the switching behavior in multilayered systems and spin valves, which show the Giant Magnetoresistance (GMR) effect. We studied patterned Ta/Ni_80Fe_20/Cu/Ni_80Fe_20/FeMn spin valves. Similar studies were performed on single Ni_80Fe_20 films, which show the anisotropic magnetoresistance (AMR) effect. First, we have found that the magnetoresistance effect itself
Philips Journal of Research, 1998
The technology of magnetoresistive element (MRE) fabrication and integration as well as some expe... more The technology of magnetoresistive element (MRE) fabrication and integration as well as some experimental results on the performance of anisotropic and giant magnetoresistive elements are discussed. Most emphasis is put on isolated MREs in specially designed test structures, although results on completed heads will also be discussed. Aspects such as output signal level, noise level, distortion and magnetic stability are
Applied Physics Letters - APPL PHYS LETT, 1994
We present magnetoresistance measurements on Ni80Fe20/Cu/Ni80Fe20/Fe50Mn50 spin valves with cross... more We present magnetoresistance measurements on Ni80Fe20/Cu/Ni80Fe20/Fe50Mn50 spin valves with crossed anisotropies: the easy magnetization direction of the unbiased Ni80Fe20 layer is perpendicular to the exchange biasing field which effectively works on the second Ni80Fe20 layer due to the interaction with the Fe50Mn50 layer. The hysteresis in the low-field magnetoresistance is less than 0.03 kA/m, which is ten times smaller than the hysteresis for similar materials with parallel anisotropies. The sensitivity (∂R/R∞)/∂H ranges from 8% to 18%/(kA/m), depending on the preparational method. To our knowledge this combination of very high sensitivity and very low coercivity has not been reported before.
Sensors and Actuators A: Physical, 1997
Journal of Magnetism and Magnetic Materials, 2000
Journal of Magnetism and Magnetic Materials, 1996
Journal of Applied Physics, 1992
The gas flow dynamics of laser ablation plumes is investigated experimentally and theoretically. ... more The gas flow dynamics of laser ablation plumes is investigated experimentally and theoretically. Experimentally, angular-resolved time-of-flight (ARTOF) measurements are performed on a model system (laser etching of copper in a chlorine environment). The TOF spectra ...
Journal of Applied Physics, 1997
Journal of Applied Physics, 1999
Abstract Spin valves are widely studied due to their application as magnetoresistive material in ... more Abstract Spin valves are widely studied due to their application as magnetoresistive material in magnetic recording heads and other magnetic field sensors. An important film property is the interlayer coupling field (called offset field H o or ferromagnetic coupling field H f). It ...
Journal of Applied Physics, 1997
Microfabricated magnetoresistive elements based on either the anisotropic or the giant magnetores... more Microfabricated magnetoresistive elements based on either the anisotropic or the giant magnetoresistance effect were tested for their frequency dependent resistance noise behavior at room temperature in a dc magnetic field, using a dc sense current. Thermal resistance noise was the dominant noise source above about 10 kHz. At low frequencies the resistance noise was found to be dominated by a
Journal of Applied Physics, 2010
IEEE Transactions on Magnetics, 2004
... Katrina Rook ... With a thinner NiFeCr a relatively thicker CoFe is needed in order to reach ... more ... Katrina Rook ... With a thinner NiFeCr a relatively thicker CoFe is needed in order to reach the high MR% boundary and vice-versa for a thinner CoFe. From the studies of the bilayer structure, the nonlinear Rs versus CoFe thickness has been observed. ...
IEEE Transactions on Magnetics, 1994
... In a yoke type thin film head the MRE property that mainly influences ?l is the product p,.t ... more ... In a yoke type thin film head the MRE property that mainly influences ?l is the product p,.t where t is the thickness of the active layer in the MRE and pr is its relative permeability [12]. ... "Analytical description of thin film yoke magneto-resistive heads", Philips J. Res. 36, pp. ...
IEEE Transactions on Magnetics, 1995
The conductivity of sputtered Ta/Cu/Ta and Ta/Ni80Fe 20/Ta thin films was measured for a film thi... more The conductivity of sputtered Ta/Cu/Ta and Ta/Ni80Fe 20/Ta thin films was measured for a film thickness ranging from 20 to 1500 Å. The measured data were analyzed using a semi-classical model for the electron transport, that includes grain boundary scattering, It was found that in these films grain boundaries are an important source of electron scattering, in Ni80Fe20 leading to
IEEE Transactions on Magnetics, 1995
Exchange-biased spin valve multilayers [ 11 are viable can-didates for application in thin film m... more Exchange-biased spin valve multilayers [ 11 are viable can-didates for application in thin film magnetic recording heads for hard disk [2] or tape applications [3], due to their sensitiv-ity to small magnetic fieids, in particular when permalloy (NigoFe20) is used as the' sensitive ...
We demonstrate that /f noise is a sensitive probe for the micromagnetic aspects of the switching ... more We demonstrate that /f noise is a sensitive probe for the micromagnetic aspects of the switching behavior in multilayered systems and spin valves, which show the Giant Magnetoresistance (GMR) effect. We studied patterned Ta/Ni_80Fe_20/Cu/Ni_80Fe_20/FeMn spin valves. Similar studies were performed on single Ni_80Fe_20 films, which show the anisotropic magnetoresistance (AMR) effect. First, we have found that the magnetoresistance effect itself transforms magnetic fluctuations into resistance fluctuations contributing to 1/f noise. This leads to an increased noise output as the sensitivity ( ~ dR/dH) of the spin valve is increased. Second, we have found a relation between the /f noise amplitude and micromagnetic effects (domain wall nucleation and pinning, ripple, etc.). These potential noise sources can be visualised by means of Kerr and Lorentz microscopy. Third, the role of interfacial scattering, the free and the exchange biased NiFe layer (in a crossed or parallel anisotropy configuration) and an incomplete exchange biasing is discussed. In order to seperate their contributions, we have performed noise experiments for various layer thickne! sses and compositions.