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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Origin of the orientation ratio in sputtered longitudinal media

B. G. Demczyk, J. N. Zhou, G. Choe, E. Stach, E. C. Nelson, and U. Dahmen

J. Appl. Phys. 93, 7393 (2003); http://dx.doi.org/10.1063/1.1558236 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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The surface morphology, thin film microstructure, and crystallography of sputtered longitudinal media were examined by atomic force and transmission electron microscopy. It was found that surface features along the texture lines in addition to the line density affect the measured orientation ratio. In addition, c-axis alignment along the texture line direction was established. These results point to magnetocrystalline anisotropy associated with the c axis as a major contributor to a high orientation ratio in these materials. © 2003 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
68.65.Ac Multilayers
75.30.Gw Magnetic anisotropy
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)
68.37.Lp Transmission electron microscopy (TEM)

Anomalously large damping in magnetization reversal

Xiaobin Wang and H. Neal Bertram

J. Appl. Phys. 93, 7396 (2003); http://dx.doi.org/10.1063/1.1540048 (3 pages) | Cited 5 times

Online Publication Date: 9 May 2003

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Anomalously large damping has been obtained for magnetic reversal based upon a model that adds damping and thermal fluctuations to normal modes around equilibrium. This accelerated reversal behavior is due to a large damping rate associated with damped nonlinear oscillation motion away from equilibrium. We suggest that this result may shed light on understanding the large damping rates observed in some magnetic reversal experiments. © 2003 American Institute of Physics.
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75.60.Jk Magnetization reversal mechanisms

Analysis of thermal effects in thin-film media

Qingzhi Peng and H. J. Richter

J. Appl. Phys. 93, 7399 (2003); http://dx.doi.org/10.1063/1.1540049 (3 pages) | Cited 6 times

Online Publication Date: 9 May 2003

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A simple solution for dynamic coercivity was derived to study the effect of the second-order anisotropy K2 on thermally assisted magnetization reversals for both perpendicular and longitudinal media. For longitudinal media, the energy barrier is calculated by adopting the approach of approximate expansion of total energy. In the balance between the thermal stability and writability, only the media with easy axis well oriented along the field direction will benefit from the effect of K2 due to a relatively larger increase in the energy barrier than in the intrinsic switching field. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.60.Jk Magnetization reversal mechanisms
75.30.Gw Magnetic anisotropy
68.60.Dv Thermal stability; thermal effects

Antiferromagnetically coupled media performance

Kai Tang, Mary Doerner, Qi-Fan Xiao, Li Tang, Mark Mercado, Jizhong He, Roeshan Prichard, and Philip Rice

J. Appl. Phys. 93, 7402 (2003); http://dx.doi.org/10.1063/1.1555969 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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Magnetic and recording properties of antiferromagnetically coupled (AFC) media are studied in comparison to conventional media. AFC media have superior magnetic recording properties compared to conventional media in terms of media signal to noise ratio (S0NR) increase and transition pulse width (PW50) reduction. Such improvements are most significant for media with (11.0) texture, small underlayer grain size, and low dispersion of the crystallographic texture. AFC media with (10.0) texture do not perform as well. In particular, AFC media have wider PW50 than conventional media in this orientation. For (11.0) textured media, the large underlayer grain size reduces media SNR improvement of AFC media while exchange field reduction is the major drawback of the deteriorated crystallographic texture. © 2003 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.50.Ee Antiferromagnetics
75.30.Et Exchange and superexchange interactions
68.55.-a Thin film structure and morphology

Thermally induced magnetization reversal in antiferromagnetically coupled media

Rok Dittrich, Thomas Schrefl, Dieter Suess, Werner Scholz, Hermann Forster, and Josef Fidler

J. Appl. Phys. 93, 7405 (2003); http://dx.doi.org/10.1063/1.1558237 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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The calculation of energy barriers between stable equilibrium states in strongly interacting systems requires the calculation of saddle points in high dimensional energy landscapes. We combine the nudged elastic band method with finite element micromagnetics to calculate optimal paths, giving a global view of thermal switching in antiferromagnetically coupled media. Energy barriers and transition rates can be estimated from the saddle points and the energy minima along this path. We investigate the dependence of the energy barrier on the strength of the antiferromagnetic coupling and study the reversal in the data bit transition region. Below 1.1 mJ/m2 a two step reversal occurs passing a metastable state. Above 1.1 mJ/m2 this metastable state disappears and the energy barrier is constant for a coupling strength greater than 1.5 mJ/m2. © 2003 American Institute of Physics.
Show PACS
75.60.Jk Magnetization reversal mechanisms
75.50.Ee Antiferromagnetics
75.50.Ss Magnetic recording materials
75.10.Lp Band and itinerant models
75.30.Et Exchange and superexchange interactions
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Improvement of exchange bias field by introduction of oxygen during deposition of Ru layer in antiferromagnetic coupled media

D. D. Djayaprawira, H. Domon, S. Yoshimura, and M. Takahashi

J. Appl. Phys. 93, 7408 (2003); http://dx.doi.org/10.1063/1.1555970 (3 pages)

Online Publication Date: 9 May 2003

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It is shown that the antiferromagnetic exchange coupling J in antiferromagnetic coupling (AFC) media using a CoCr-based magnetic layer can be increased up to 65% by introducing oxygen with pressure of 2×10−5 Torr during deposition of a Ru spacer layer. The thermal stability factor KV/kT is also increased from 91 to 106 in the same manner. The increase of J by introducing oxygen during deposition of the Ru spacer layer does not originate from improvement of the flatness of Ru interfaces, but is suggested to be due to the formation of a layer with high Co concentration at the Ru interfaces. It is concluded that the proposed method is effective in increasing the thermal stability of AFC media with a conventional structure through the improvement of J. © 2003 American Institute of Physics.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Ee Antiferromagnetics
75.30.Et Exchange and superexchange interactions
68.37.Ps Atomic force microscopy (AFM)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.65.Ac Multilayers
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