Perpendicular magnetic recording medium with multiple exchange-coupled magnetic layers having substantially similar anisotropy fields
US7550210B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 9, 2006 |
| Grant date | Jun 23, 2009 |
| Priority date | — |
| Expiry date | Sep 15, 2027 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B5/678
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A perpendicular magnetic recording medium has an “exchange-spring” type magnetic recording layer (RL) formed of two ferromagnetic layers with substantially similar anisotropy fields that are ferromagnetically exchange-coupled by a nonmagnetic or weakly ferromagnetic coupling layer. Because the write head produces a larger magnetic field and larger field gradient at the upper portion of the RL, while the field strength decreases further inside the RL, the upper ferromagnetic layer can have a high anisotropy field. The high field and field gradient near the top of the RL, where the upper ferromagnetic layer is located, reverses the magnetization of the upper ferromagnetic layer, which then assists in the magnetization reversal of the lower ferromagnetic layer. Because both ferromagnetic layers in this exchange-spring type RL have a high anisotropy field, the thermal stability of the medium is not compromised. The medium shows improved writability, i.e., a low switching field, as well as lower intrinsic media noise, over a medium with a conventional single-layer RL.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.