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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Magnetoelastic coupling constants in epitaxial Co80Pt20 films

Bin Xu and William D. Doyle

J. Appl. Phys. 93, 8459 (2003); http://dx.doi.org/10.1063/1.1540166 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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Magnetoelastic coupling constants in epitaxial hcp Co80Pt20 films with (10math0) orientation (a axis and c axis in plane) have been measured. A magnetostrictive stress tester with magnetic field up to 18 kOe was constructed based on the bending cantilever technique. The magnetoelastic coupling constants were directly extracted from the magnetostrictive stress data and no information on the mechanical properties of the Co80Pt20 film is needed. The magnetoelastic coupling constants along the a and c axes were B1′=15×106 and B2′=−80×106 erg/cc, respectively, which are much smaller than those of pure Co. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Cc Other ferromagnetic metals and alloys
75.80.+q Magnetomechanical effects, magnetostriction

Magnetic properties of Fe3C nanograins embedded in carbon matrix

Y. H. Lee, T. C. Han, and J. C. A. Huang

J. Appl. Phys. 93, 8462 (2003); http://dx.doi.org/10.1063/1.1555852 (3 pages) | Cited 10 times

Online Publication Date: 9 May 2003

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Magnetron dc cosputtering of a composite target of graphite disk plus iron rods was used in manufacturing carbon films with Fe3C nanograin inclusions. Both temperature- and field-dependent magnetizations, M(T) and M(H), were measured for samples of various carbon concentrations (from 37% to 85%). M(T) were measured in both conditions of zero-field cooling and a field cooling at H=100 Oe. Experimental results of χ(T), obtained from M(T), of zero-field cooling, were theoretically fitted by using Wolhfarth’s model of noninteracting particles with log–normal distribution function of particle size. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Tt Fine-particle systems; nanocrystalline materials
81.15.Cd Deposition by sputtering
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.55.-a Thin film structure and morphology
81.07.Bc Nanocrystalline materials

Effect of very thin Cr-based seedlayer material with different affinity for oxygen on thin film media microstructure and recording properties

S. Yoshimura, D. D. Djayaprawira, Y. Takakuwa, and M. Takahashi

J. Appl. Phys. 93, 8465 (2003); http://dx.doi.org/10.1063/1.1558101 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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To reduce the grain size and the media noise in longitudinal media, a sputtering process which includes the exposure of oxygen onto the surface of Cr-based seedlayers (CrTi15, Cr100, WCr75, WCr50, WCr25, and W100) with the thickness of 0.5 nm have been utilized. It is found that to effectively reduce the media grain size and improve the media signal-to-noise ratio, it is essential to utilize a very thin Cr-based seedlayer with a high melting point, a high affinity for oxygen, and which forms an island-like structure. A physical guideline for seedlayer material that is effective in reducing the grain size and the media noise is proposed. © 2003 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.65.Ac Multilayers

Effects of alloying additions in the CrMo underlayer on the grain size and magnetic properties of CoCrPt longitudinal media

Chih-Huang Lai, Wei-Chuan Chen, P. H. Tsai, and I. P. Ding

J. Appl. Phys. 93, 8468 (2003); http://dx.doi.org/10.1063/1.1558102 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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The alloy doping effects of the CrMo underlayer were investigated on the texture, grain size, and magnetic properties of CoCrPt longitudinal media. 5% Mn dissolving into CrMo lattices enhanced the texture of the recording layer and significantly raised the coercivity from 2200 (on the CrMo underlayer) to 3200 Oe. Further increases in the Mn content resulted in the grain growth of the recording layer, and less enhanced coercivity. The doped Zr, Ag, and Nb atoms into CrMo underlayers were segregated and led to reduction of grain size. Among them, Zr doping exhibited the most pronounced effects. © 2003 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
64.75.-g Phase equilibria

Angle dependent magnetization reversal of thin film magnetic recording media

Kevin R. Coffey, Thomas Thomson, and Jan-Ulrich Thiele

J. Appl. Phys. 93, 8471 (2003); http://dx.doi.org/10.1063/1.1540167 (3 pages) | Cited 14 times

Online Publication Date: 9 May 2003

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The results of angular measurements of the remanent switching fields for granular longitudinal and perpendicular magnetic recording media are presented and compared to idealized models of magnetic switching. Co alloy longitudinal and perpendicular recording media are found primarily to have a Stoner–Wohlfarth switching character at vibrating sample magnetometer time scales. Since the Stoner–Wohlfarth model does not consider the effects of thermal activation, the angular dependence of the time independent switching field Hswro(θ) was determined from a Sharrock analysis. This approach shows a closer agreement between experimental data and model. For the case of a representative high density longitudinal recording medium, we additionally investigate the switching field distribution. © 2003 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.60.Jk Magnetization reversal mechanisms
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Thermal stability of coupled ferromagnetic and superparamagnetic particles

Vladimir L. Safonov and H. Neal Bertram

J. Appl. Phys. 93, 8474 (2003); http://dx.doi.org/10.1063/1.1555853 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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We consider a single-domain ferromagnetic particle with uniaxial anisotropy coupled to a single-domain soft ferromagnetic particle (superparamagnetic particle). The problem of thermally agitated magnetization reversal in this case can be reduced to the random magnetization dynamics of the first particle with an effectively larger anisotropy field. The magnetic external field is also altered in a manner that depends on the sign of the coupling and can be either enhanced or suppressed. © 2003 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Jk Magnetization reversal mechanisms
75.30.Gw Magnetic anisotropy

Low temperature thermomagnetic print for hard disk servo writing

Hiroyuki Ikeda, Yuzo Seo, and Yoji Arita

J. Appl. Phys. 93, 8477 (2003); http://dx.doi.org/10.1063/1.1540168 (3 pages)

Online Publication Date: 9 May 2003

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Thermomagnetic print, proposed in the 1980’s, is expected to apply to hard disk drive servo writing. The print needs to be done after certification of media using magnetic head, so decomposition of lubricant on the media surface is the issue. Thermomagnetic print can be done at lower temperatures than Curie point, utilizing the small change of Hc by heating. But since the print should be done in short term to avoid thermal diffusion, the effective Hc is much higher than the static Hc. In the process, proposed in this article, the dynamic effect is suppressed. A part of the printing field is generated in a very short period, so the dynamic Hc at nonheated areas is also increased and the divergence of Hc is kept large enough. For the experiment, KrF excimer laser was used as the light source. Si mask was faced on the media with 0.5 μm spacing. For printing narrow pattern less than 1 μm in width on media of Hc 3.4 kOe, the optimum laser power was 90 mJ/cm2 and the optimum printing field was 3.1 kG including 1.0 kG of 0.1 ms pulse field. The signal-to-noise ratio was 16 dB, which was 3 dB better than the existing process. The maximum temperature is near 200 °C, estimated by numerical method. © 2003 American Institute of Physics.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Ss Magnetic recording materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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