Advanced laminated antiferromagnetically coupled recording media with high thermal stability

Abstract

A layered structure to improve the antiferromagnetic exchange coupling constant (J) in laminated antiferromagnetically coupled (LAC) media is proposed. This structure has a much larger thermal stability in comparison to simple LAC structures. It also improves the coercivity and decreases the remnant moment-thickness product to achieve a high resolution and a low pulse width. The recording measurements indicate that this structure has a slightly larger noise than the simple LAC structures. However, its overall signal-to-noise ratio (SNR) is comparable to that of the simple LAC structures. High SNR and much higher thermal stability make this structure suitable for ultrahigh areal densities.

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

“…Figure 3 shows the dependence of J on the oxygen pressure during deposition of the Ru spacer layer for media B, C and D. In media B, insertion of 1 nm of pure Co layers between the magnetic layers and the Ru layer significantly increases J of AFC media, which is consistent with the results obtained from other studies. [3][4][5] In comparing media B and C, it is found that J is independent of the oxygen pressure in media B. By comparing media C and D, we find that in both media J increases with an increase in oxygen pressure, reaches a maximum at about 2ϫ10 Ϫ5 Torr, then decreases.…”

“…Recent studies showed that both J and H ex can be significantly increased by inserting 1 nm of pure Co between magnetic layers and the Ru spacer layer. [3][4][5] However, this method has drawbacks, such as the requirement of two additional depositions procedures, which will increase the media manufacturing costs and increase media noise. 3 Therefore, the development of a low-cost technique to fabricate thermally stable AFC media is of importance.…”

Numerical Study of Enhanced Coercivity of a Magnetically Hard Grain With Thin Surface Layers Due to Antiferromagnetic Coupling

“…The exchange anisotropy induced by the antiferromagnetic coupling is expected to affect H c of Nd 2 Fe 14 B similarly to the cases in the previous materials [5][6][7][8][9][10]. We may enhance H c of magnets by using antiferromagnetic coupling between boundary and hard magnetic phases.…”

“…Some ferromagnetic materials couple antiferromagnetically through the RKKY interaction; Co-Ru-Co has been reported to have the strongest RKKY interaction (−5×10 −3 J/m 2 ) [8]. This phenomenon change magnetization process of the coupled substances [9] and is used as an exchange bias for memory materials [9,10]. In α-Fe(001)/Fe 3 O 4 (001), the two ferromagnetic phases directly exchange couple antiferromagnetically (antiparallelly) and their magnetization process is affected by the exchange interaction [11].…”

Noise reduction mechanisms in laminated antiferromagnetically coupled recording media

“…However, it was found that the increase of H ex is much larger even for small improvements of M s when a certain LAC structure is used. 6 This suggests that H ex is much larger than H d in LAC media.…”