Jan van Ek - Academia.edu (original) (raw)

Papers by Jan van Ek

Research paper thumbnail of Beveled writing pole of a perpendicular writing element

Research paper thumbnail of Writer structure with assisted bias

Research paper thumbnail of Spin valve magnetoresistive sensor using permanent magnet biased artificial antiferromagnet layer

Research paper thumbnail of Multi-bit memory with selectable magnetic layer

Research paper thumbnail of Writing element with no return path

Research paper thumbnail of Method of forming a beveled writing pole of a perpendicular writing element

Research paper thumbnail of Micromagnetic recording model of writer geometry effects at skew

Journal of Applied Physics, 2006

The effects of the pole-tip geometry at the air-bearing surface on perpendicular recording at a s... more The effects of the pole-tip geometry at the air-bearing surface on perpendicular recording at a skew angle are examined through modeling and spin-stand test data. Head fields generated by the finite element method were used to record transitions within our previously described micromagnetic recording model. Write-field contours for a variety of square, rectangular, and trapezoidal pole shapes were evaluated to determine the impact of geometry on field contours. Comparing results for recorded track width, transition width, and media signal to noise ratio at 0°and 15°skew demonstrate the benefits of trapezoidal and reduced aspect-ratio pole shapes. Consistency between these modeled results and test data is demonstrated.

Research paper thumbnail of Giant magnetoresistance properties of patterned IrMn exchange biased spin valves

Journal of Applied Physics, 1999

Giant magnetoresistance (GMR) responses were studied in micron-sized IrMn pinned spin valve strip... more Giant magnetoresistance (GMR) responses were studied in micron-sized IrMn pinned spin valve stripes. As the stripe height is decreased both the pinning field and free layer bias field increase while the GMR ratio stays almost constant. The free layer coercivity becomes zero for the ...

Research paper thumbnail of Enhanced magnetic stability in spin valves with synthetic antiferromagnet

Journal of Applied Physics, 2000

The nucleation field in a synthetic antiferromagnet has been studied as a function of the stabili... more The nucleation field in a synthetic antiferromagnet has been studied as a function of the stabilization strength. The results can be used to predict the magnetic stability in a GMR read-back head, that utilizes a synthetic antiferromagnet instead of a single pinned layer. Experimental studies showed substantially improved magnetic stability at higher temperature in synthetic antiferromagnet spin valves.

Research paper thumbnail of Effect of Storage Layer on Writeability of a Perpendicular Magnetic Recording Head

IEEE Transactions on Magnetics, 2007

The effect of the storage layer on the writeability of a magnetic head for perpendicular recordin... more The effect of the storage layer on the writeability of a magnetic head for perpendicular recording was studied through micromagnetic and finite-element-method modeling. The results suggest that the permeability of the storage layer of double-layer perpendicular recording medium monotonically increases with the intergranular exchange. Increase of the storage layer permeability improves the writeability of the single-pole recording head and the gradient of the write field in the storage layer.

Research paper thumbnail of Differential CPP reader for perpendicular magnetic recording

Research paper thumbnail of High-efficiency single-turn write head for high-speed recording

Research paper thumbnail of The XXVI Magnetic Recording Conference 2015 Foreword

IEEE Transactions on Magnetics, 2016

On behalf of the organizing committee of the XXVI Magnetic Recording Conference (TMRC) 2015, we a... more On behalf of the organizing committee of the XXVI Magnetic Recording Conference (TMRC) 2015, we are pleased to present selected invited papers from the conference in this issue of the IEEE Transactions on Magnetics. The conference was held at the University of Minnesota, Minneapolis, MN, USA, from August 17 to 19, 2015. The hard work and hospitality of the hosting institution and all the committee members in making this event so successful are greatly appreciated. TMRC is an annual meeting of the magnetic recording community, organized under the auspices of the IEEE Magnetics Society, with a format of all invited oral presentations. An evening poster session of the invited and contributed papers enhances further discussion between the speakers and the participants.

Research paper thumbnail of The Physics of Ultra-High-Density Magnetic Recording

Springer Series in Surface Sciences, 2001

... Reductions in track width and bit length have put significant pressure on head performance ..... more ... Reductions in track width and bit length have put significant pressure on head performance ... Christopher B. Murray 249 10 Theory of Magnetotransport for Magnetic Recording William H. Butler ... S. Bloomington, MN 55435 Johannes van Ek Segate Technology 7801 Computer Ave ...

Research paper thumbnail of A Monte Carlo Approach to Modeling Thermal Decay in Perpendicular Recording Media

Digital Corporation-A procedure is developed to study the evolution of high anisotropy magnetic r... more Digital Corporation-A procedure is developed to study the evolution of high anisotropy magnetic recording media due to thermally activated grain reversal [1]. Single-domain grains evolve by passing through a sequence of relatively long-lived metastable states punctuated by abrupt reversals. Solutions to the rate equations are obtained using a stochastic integration procedure that calculates the time between successive reversals. Transition rates are formulated from the Arrhenius-Neel expression in terms of the material parameters, the temperature and the applied field. The method is applied to study the rate dependence of finite temperature MH loops and the thermal degradation of a recorded bit pattern in perpendicular recording media. A significant advantage of the method is its ability to extend simulations over time intervals many orders of magnitude greater than is feasible using standard micromagnetics with relatively modest computational effort. [1] T.

Research paper thumbnail of Magnetic writing pole and a perpendicular writing element

Research paper thumbnail of Introduction to Micromagnetic Recording Physics

Springer Series in Surface Sciences, 2001

Extremely effective reduction of physical dimensions in the recording head through photolithograp... more Extremely effective reduction of physical dimensions in the recording head through photolithography techniques, in combination with tremendous development in thin film recording media, has led to a spectacular increase in areal density in the magnetic recording industry. Since the fundamental length scale (exchange length) in ferromagnetic materials is on the order of 10-8 meter, the small physical dimensions have made

Research paper thumbnail of Micromagnetic perpendicular recording model: soft magnetic underlayer and skew effect

Journal of Magnetism and Magnetic Materials, 2001

Two major issues with perpendicular recording on double-layer media were identified and illustrat... more Two major issues with perpendicular recording on double-layer media were identified and illustrated with a comprehensive micromagnetic recording model. Currently, side-writing with a single pole writer at a skew angle, and the detrimental effect of the presence of the soft under layer during play back of the recorded signal, pose serious limitations on the feasibility of a perpendicular recording system at ultra-high areal density.

Research paper thumbnail of Micromagnetic modeling of low noise perpendicular media

Journal of Applied Physics, 2002

The effect of magnetic anisotropy constants and inter-granular exchange coupling on properties of... more The effect of magnetic anisotropy constants and inter-granular exchange coupling on properties of hcp CoCrX perpendicular media was studied by micromagnetic modeling. It was found that the second anisotropy constant K2 reduces the energy barrier, coercivity HC, saturation field HS and, as a result, promotes writeability of the media for fixed anisotropy field HK. HC inversely decreases with the increase of K2/K1 ratio. Exchange coupling modifies a domain structure of the media in a virgin state and slope of hysteresis loop by reducing the coercivity and saturation field, and marginally increasing the nucleation field. Magnetic domains were found even in the decoupled media. The minimal domain size is about 2.5⋅dG, where dG is an average grain size of the media. The domain size increases exponentially with the inter-granular exchange. The transition parameter and dc noise is reduced with increased exchange coupling. At a specific exchange coupling the dependence of the transition parameter on the exchange ...

Research paper thumbnail of Variation of magnetoresistive sensitivity maps of patterned giant magnetoresistance sensors

Journal of Applied Physics, 2001

A scanning probe microscope which combines probe contacts for the supply of current with a magnet... more A scanning probe microscope which combines probe contacts for the supply of current with a magnetic force microscope (MFM) for fully automated imaging of electrically active, patterned sensor-like devices across a wafer was developed. This was used for magnetoresistive ...

Research paper thumbnail of Beveled writing pole of a perpendicular writing element

Research paper thumbnail of Writer structure with assisted bias

Research paper thumbnail of Spin valve magnetoresistive sensor using permanent magnet biased artificial antiferromagnet layer

Research paper thumbnail of Multi-bit memory with selectable magnetic layer

Research paper thumbnail of Writing element with no return path

Research paper thumbnail of Method of forming a beveled writing pole of a perpendicular writing element

Research paper thumbnail of Micromagnetic recording model of writer geometry effects at skew

Journal of Applied Physics, 2006

The effects of the pole-tip geometry at the air-bearing surface on perpendicular recording at a s... more The effects of the pole-tip geometry at the air-bearing surface on perpendicular recording at a skew angle are examined through modeling and spin-stand test data. Head fields generated by the finite element method were used to record transitions within our previously described micromagnetic recording model. Write-field contours for a variety of square, rectangular, and trapezoidal pole shapes were evaluated to determine the impact of geometry on field contours. Comparing results for recorded track width, transition width, and media signal to noise ratio at 0°and 15°skew demonstrate the benefits of trapezoidal and reduced aspect-ratio pole shapes. Consistency between these modeled results and test data is demonstrated.

Research paper thumbnail of Giant magnetoresistance properties of patterned IrMn exchange biased spin valves

Journal of Applied Physics, 1999

Giant magnetoresistance (GMR) responses were studied in micron-sized IrMn pinned spin valve strip... more Giant magnetoresistance (GMR) responses were studied in micron-sized IrMn pinned spin valve stripes. As the stripe height is decreased both the pinning field and free layer bias field increase while the GMR ratio stays almost constant. The free layer coercivity becomes zero for the ...

Research paper thumbnail of Enhanced magnetic stability in spin valves with synthetic antiferromagnet

Journal of Applied Physics, 2000

The nucleation field in a synthetic antiferromagnet has been studied as a function of the stabili... more The nucleation field in a synthetic antiferromagnet has been studied as a function of the stabilization strength. The results can be used to predict the magnetic stability in a GMR read-back head, that utilizes a synthetic antiferromagnet instead of a single pinned layer. Experimental studies showed substantially improved magnetic stability at higher temperature in synthetic antiferromagnet spin valves.

Research paper thumbnail of Effect of Storage Layer on Writeability of a Perpendicular Magnetic Recording Head

IEEE Transactions on Magnetics, 2007

The effect of the storage layer on the writeability of a magnetic head for perpendicular recordin... more The effect of the storage layer on the writeability of a magnetic head for perpendicular recording was studied through micromagnetic and finite-element-method modeling. The results suggest that the permeability of the storage layer of double-layer perpendicular recording medium monotonically increases with the intergranular exchange. Increase of the storage layer permeability improves the writeability of the single-pole recording head and the gradient of the write field in the storage layer.

Research paper thumbnail of Differential CPP reader for perpendicular magnetic recording

Research paper thumbnail of High-efficiency single-turn write head for high-speed recording

Research paper thumbnail of The XXVI Magnetic Recording Conference 2015 Foreword

IEEE Transactions on Magnetics, 2016

On behalf of the organizing committee of the XXVI Magnetic Recording Conference (TMRC) 2015, we a... more On behalf of the organizing committee of the XXVI Magnetic Recording Conference (TMRC) 2015, we are pleased to present selected invited papers from the conference in this issue of the IEEE Transactions on Magnetics. The conference was held at the University of Minnesota, Minneapolis, MN, USA, from August 17 to 19, 2015. The hard work and hospitality of the hosting institution and all the committee members in making this event so successful are greatly appreciated. TMRC is an annual meeting of the magnetic recording community, organized under the auspices of the IEEE Magnetics Society, with a format of all invited oral presentations. An evening poster session of the invited and contributed papers enhances further discussion between the speakers and the participants.

Research paper thumbnail of The Physics of Ultra-High-Density Magnetic Recording

Springer Series in Surface Sciences, 2001

... Reductions in track width and bit length have put significant pressure on head performance ..... more ... Reductions in track width and bit length have put significant pressure on head performance ... Christopher B. Murray 249 10 Theory of Magnetotransport for Magnetic Recording William H. Butler ... S. Bloomington, MN 55435 Johannes van Ek Segate Technology 7801 Computer Ave ...

Research paper thumbnail of A Monte Carlo Approach to Modeling Thermal Decay in Perpendicular Recording Media

Digital Corporation-A procedure is developed to study the evolution of high anisotropy magnetic r... more Digital Corporation-A procedure is developed to study the evolution of high anisotropy magnetic recording media due to thermally activated grain reversal [1]. Single-domain grains evolve by passing through a sequence of relatively long-lived metastable states punctuated by abrupt reversals. Solutions to the rate equations are obtained using a stochastic integration procedure that calculates the time between successive reversals. Transition rates are formulated from the Arrhenius-Neel expression in terms of the material parameters, the temperature and the applied field. The method is applied to study the rate dependence of finite temperature MH loops and the thermal degradation of a recorded bit pattern in perpendicular recording media. A significant advantage of the method is its ability to extend simulations over time intervals many orders of magnitude greater than is feasible using standard micromagnetics with relatively modest computational effort. [1] T.

Research paper thumbnail of Magnetic writing pole and a perpendicular writing element

Research paper thumbnail of Introduction to Micromagnetic Recording Physics

Springer Series in Surface Sciences, 2001

Extremely effective reduction of physical dimensions in the recording head through photolithograp... more Extremely effective reduction of physical dimensions in the recording head through photolithography techniques, in combination with tremendous development in thin film recording media, has led to a spectacular increase in areal density in the magnetic recording industry. Since the fundamental length scale (exchange length) in ferromagnetic materials is on the order of 10-8 meter, the small physical dimensions have made

Research paper thumbnail of Micromagnetic perpendicular recording model: soft magnetic underlayer and skew effect

Journal of Magnetism and Magnetic Materials, 2001

Two major issues with perpendicular recording on double-layer media were identified and illustrat... more Two major issues with perpendicular recording on double-layer media were identified and illustrated with a comprehensive micromagnetic recording model. Currently, side-writing with a single pole writer at a skew angle, and the detrimental effect of the presence of the soft under layer during play back of the recorded signal, pose serious limitations on the feasibility of a perpendicular recording system at ultra-high areal density.

Research paper thumbnail of Micromagnetic modeling of low noise perpendicular media

Journal of Applied Physics, 2002

The effect of magnetic anisotropy constants and inter-granular exchange coupling on properties of... more The effect of magnetic anisotropy constants and inter-granular exchange coupling on properties of hcp CoCrX perpendicular media was studied by micromagnetic modeling. It was found that the second anisotropy constant K2 reduces the energy barrier, coercivity HC, saturation field HS and, as a result, promotes writeability of the media for fixed anisotropy field HK. HC inversely decreases with the increase of K2/K1 ratio. Exchange coupling modifies a domain structure of the media in a virgin state and slope of hysteresis loop by reducing the coercivity and saturation field, and marginally increasing the nucleation field. Magnetic domains were found even in the decoupled media. The minimal domain size is about 2.5⋅dG, where dG is an average grain size of the media. The domain size increases exponentially with the inter-granular exchange. The transition parameter and dc noise is reduced with increased exchange coupling. At a specific exchange coupling the dependence of the transition parameter on the exchange ...

Research paper thumbnail of Variation of magnetoresistive sensitivity maps of patterned giant magnetoresistance sensors

Journal of Applied Physics, 2001

A scanning probe microscope which combines probe contacts for the supply of current with a magnet... more A scanning probe microscope which combines probe contacts for the supply of current with a magnetic force microscope (MFM) for fully automated imaging of electrically active, patterned sensor-like devices across a wafer was developed. This was used for magnetoresistive ...