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15 May 2002

Volume 91, Issue 10, pp. 6227-8917

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Study of magnetic field determined from vanishing rotational hysteresis loss in CoCrPtB perpendicular thin film media

Shin Saito, Yoshihiro Sato, Fumikazu Hoshi, David D. Djayaprawira, and Migaku Takahashi

J. Appl. Phys. 91, 8351 (2002); http://dx.doi.org/10.1063/1.1452278 (3 pages) | Cited 3 times

Online Publication Date: 13 May 2002

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The magnetic field determined from vanishing rotational hysteresis loss of CoCrPtB perpendicular thin film media was experimentally investigated. It was clarified that (1) in Co72Cr16Pt8B4 media with dmag of less than 200 nm and Co64Cr24Pt8B4 media with dmag of less than 100 nm, a homogeneous structure was realized, except for the existence of an initial growth region. (2) For both media, the perpendicular rotational hysteresis loss, Wr, the maximum field of Wr, Hp, and the field where Wr=0, HWr=0, increased with an increase in dmag. (3) For both media, HWr=0/Hkgrain increased with an increase in dmag and saturated at a magnitude of about 1. (4) For the medium with thin magnetic film thickness, at applied field of HWr=0<H<Hkgrain, a multidomain state was realized in the torque measurement in spite of no observation of loss of rotational hysteresis. This is considered to be due to the existence of thermal agitation between the multidomains. © 2002 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.70.Kw Domain structure (including magnetic bubbles and vortices)

Magnetization processes of storage and back layers in double-layered perpendicular magnetic recording media observed using anomalous and planar Hall effects

Shigeki Nakagawa, Ichiro Sasaki, and Masahiko Naoe

J. Appl. Phys. 91, 8354 (2002); http://dx.doi.org/10.1063/1.1456418 (3 pages) | Cited 16 times

Online Publication Date: 13 May 2002

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An anomalous Hall effect (AHE) and a planar Hall effect (PHE) represent a perpendicular component and an in-plane component of the magnetization in the double-layered media. Since AHE and PHE have different symmetries regarding to the applied magnetic field H, it is easy to distinguish the AHE component, which is proportional to M, and PHE component, which is proportional to M2, from the measured Hall voltage VH. The Hall voltage of the double-layered film composed of Co–Cr–Ta and Ni–Fe layers was observed when the magnetic field is applied at an angle (α) of 30° from the normal to the film plane. The perpendicular and the in-plane components, which are regarded as the magnetization process of Co–Cr–Ta and that of the Ni–Fe layer, respectively, can be easily determined from these characteristics. The Hall measurement is useful to study the magnetization characteristics in the double-layered media. © 2002 American Institute of Physics.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.50.Ss Magnetic recording materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.61.At Metal and metallic alloys

Thermal annealing effect on FeCoB soft underlayer for perpendicular magnetic recording

Jun Yu, Chunghee Chang, Duane Karns, Ganping Ju, Yukiko Kubota, Walter Eppler, Charles Brucker, and Dieter Weller

J. Appl. Phys. 91, 8357 (2002); http://dx.doi.org/10.1063/1.1452279 (3 pages) | Cited 10 times

Online Publication Date: 13 May 2002

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We study the noise performance of amorphous FeCoB soft underlayers (SULs) with radial magnetic anisotropy. 200 nm thick FeCoB films are sputter deposited and optionally postannealed for 8 s at different annealing powers. The correlation of SUL read-back noise with the magnetic and structural properties is studied using spin stand testing, in-plane magneto-optical Kerr effect measurements, magnetic force microscopy, and x-ray diffraction. The effects of annealing to achieve low read-back noise are examined. It is found that as-prepared films show large dc noise associated with stripe domains due to stress-induced perpendicular anisotropy. Thermal annealing reduces the internal stress and the films become magnetically anisotropic in the radial direction. The SUL-induced dc noise drops to the electronic noise floor. dc noise is found to decrease with an increase in annealing power until the films start to crystallize. © 2002 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.30.Gw Magnetic anisotropy
61.72.Cc Kinetics of defect formation and annealing
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
68.55.-a Thin film structure and morphology
78.20.Ls Magneto-optical effects
68.37.Rt Magnetic force microscopy (MFM)
68.60.Bs Mechanical and acoustical properties
75.70.Kw Domain structure (including magnetic bubbles and vortices)

HITPERM soft magnetic underlayers for perpendicular thin film media

S. Kumar, T. Ohkubo, and D. E. Laughlin

J. Appl. Phys. 91, 8360 (2002); http://dx.doi.org/10.1063/1.1452280 (3 pages) | Cited 4 times

Online Publication Date: 13 May 2002

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In this work, a class of nanocrystalline alloys, HITPERM (Fe, Co)–M–B–Cu (M=Zr, Hf, Nb, and etc.) found to exhibit excellent soft–magnetic properties in bulk were used as soft–magnetic underlayers for perpendicular thin film media. A Ti intermediate layer was used to promote a (00⋅2) texture and exchange de-couple the magnetic layer (CoCrPt) from the soft-magnetic underlayer. Specimens were deposited at both room and elevated temperature (∼ 250 °C). The results of x-ray diffraction and transmission electron microscope structural studies, along with magnetic properties are presented. © 2002 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
68.55.-a Thin film structure and morphology
75.50.Tt Fine-particle systems; nanocrystalline materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Ss Magnetic recording materials
75.30.Et Exchange and superexchange interactions

Recording, noise, and medium microstructure in perpendicular recording with a soft magnetic underlayer

Lijie Guan and Jian-Gang Zhu

J. Appl. Phys. 91, 8363 (2002); http://dx.doi.org/10.1063/1.1454985 (3 pages) | Cited 11 times

Online Publication Date: 13 May 2002

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A micromagnetic model for studying recording and noise characteristics in perpendicular media with a soft magnetic underlayer has been developed. The single pole head and soft magnetic underlayer are modeled with two-dimensional meshes and the medium is modeled with a three-dimensional granular structure. Utilizing the model, the dependence of recording characteristics on a medium microstructure, especially the intergranular exchange coupling, and write field is investigated. © 2002 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
68.60.Dv Thermal stability; thermal effects

Three-dimensional modeling of perpendicular reading with a soft underlayer

T. A. Roscamp, E. D. Boerner, and G. J. Parker

J. Appl. Phys. 91, 8366 (2002); http://dx.doi.org/10.1063/1.1452281 (3 pages) | Cited 17 times

Online Publication Date: 13 May 2002

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A three-dimensional (3D) reciprocity based model of the perpendicular read process with a soft underlayer is presented. In 3D with finite track width, the read flux does not decay to zero because flux is always entering the reader from the field caused by a nonvanishing curl of the magnetization. As the reader is moved off track, the signal amplitude and resolution decrease, and at some off track position there is a reversal in the sign. A comparison of the reciprocity based reader model with a micromagnetic CPP reader model shows excellent agreement both on and off track. © 2002 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Ak Magnetic properties of monolayers and thin films

Write field analysis in perpendicular recording using three-dimensional micromagnetic simulation

K. Gao and H. N. Bertram

J. Appl. Phys. 91, 8369 (2002); http://dx.doi.org/10.1063/1.1447485 (3 pages) | Cited 14 times

Online Publication Date: 13 May 2002

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A three-dimensional micromagnetic perpendicular recording model is developed to study the effect of magnetic properties and head geometry on the write head field. For parameters characteristic of 200 Gbit/in.2, the maximum write field is about 0.73 Bs. Thirty percent of this field is due to neck saturation. Calculated head field gradients at track center agree well with the theoretical Westmijze field. The maximum write field is independent of the SUL thickness for thicknesses greater than the track width. At an SUL thickness of half the track width, the field decreases by 10%, and thereafter decreases rapidly. © 2002 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

The effect of media background on reading and writing in perpendicular recording

P. A. A. van der Heijden, D. W. Karns, T. W. Clinton, S. J. Heinrich, S. Batra, D. C. Karns, T. A. Roscamp, E. D. Boerner, and W. R. Eppler

J. Appl. Phys. 91, 8372 (2002); http://dx.doi.org/10.1063/1.1447536 (3 pages) | Cited 16 times

Online Publication Date: 13 May 2002

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The effect of stray fields from the recording layer on the reading and writing process has been studied for a perpendicular recording system. The system consists of a single pole writer with a wide return pole, a conventional spin-valve reader and a double layer recording medium. A writer- and reader-induced asymmetry is observed in the recording process for a dc erased background. The asymmetry is interpreted as stray fields of the dc background giving rise to reader saturation and an offset in the current driven inductive write field. © 2002 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Micromagnetic modeling of low noise perpendicular media

Alexander Shukh and Johannes van Ek

J. Appl. Phys. 91, 8375 (2002); http://dx.doi.org/10.1063/1.1447537 (3 pages) | Cited 6 times

Online Publication Date: 13 May 2002

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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 almost disappears, approaching a minimum value of dG/3. © 2002 American Institute of Physics.
Show PACS
75.30.Gw Magnetic anisotropy
75.50.Ss Magnetic recording materials
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure

Effect of intergranular interactions on thermal energy barrier distribution in perpendicular media

Hong Zhou, H. Neal Bertram, and Manfred E. Schabes

J. Appl. Phys. 91, 8378 (2002); http://dx.doi.org/10.1063/1.1452282 (3 pages) | Cited 7 times

Online Publication Date: 13 May 2002

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Micromagnetic simulations have been performed to simulate dynamic hysteresis loops in perpendicular media. Thermal energy barrier distributions have been calculated. For a fixed percentage of magnetization switched, a linear variation between the scaled applied field Ha(t)/HK and ln(f0t)1/2 is found. Without including intergranular magnetostatic interactions, intergranular exchange coupling reduces the thermal energy barrier distribution width, compared to the physical volume distribution width. However, the magnetostatic interactions increase the energy barrier width substantially. The increase is significantly reduced at smaller magnetostatic interactions. For the effective volume of 50% magnetization switched (V50), the results show V50=math almost independent of intergranular magnetostatic and exchange interactions. © 2002 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Et Exchange and superexchange interactions
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
68.55.-a Thin film structure and morphology

Micromagnetic study of effect of media intergranular exchange interaction in perpendicular recording

Lei Wang, Shaoping Li, James H. Giusti, and Juan Fernandez-de-Castro

J. Appl. Phys. 91, 8381 (2002); http://dx.doi.org/10.1063/1.1452283 (3 pages) | Cited 3 times

Online Publication Date: 13 May 2002

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A micromagnetic study is performed for the writing and reading processes in perpendicular recording at high areal densities. In particular, the effect of intergranular exchange interactions in media is examined. Calculations are done for three different values of intergranular exchange coupling. The calculated media hysteresis loops show that the saturation magnetic field increases when exchange becomes weaker. The writer deep gap field is chosen to be equal to the saturation field so that proper overwrite is assured. Modeling shows that the magnetic cluster domain size becomes larger and the readback signal exhibits larger variation at its peaks when exchange constant increases. The variation of readback signal at its peaks in square wave perpendicular recording is primarily due to the variation of bit cell length of written patterns. On the other hand, transition curvature increases when exchange constant decreases. Although on-track isolated pulse width of a differentiated signal is not affected much by transition curvature, the off-track isolated pulse width is larger when transition curvature is larger. © 2002 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
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