Exchange coupled composite media for perpendicular magnetic recording

Supperparamagnetism is the fundamental factor that limits the achievable areal density in magnetic recording. Materials with extremely high magnetic anisotropy have to be used for recording media to obtain thermally stable data storage. However, the required writing field will be a serious problem for the recording media with extremely high anisotropy. Conventional perpendicular magnetic recording partially alleviates this problem by applying a soft underlayer. Due to the limitation of available materials with high saturation magnetization, the maximum writing field available is around 2.45 T. This will limit the attainable recording density to 500 Gbit/in2, which will be reached near the end of the first decade in this new century. In order to continue the success of magnetic recording, new approaches are urgently needed.;In this work, a new type of magnetic recording medium, exchange-coupled composite (ECC) medium, has been successfully developed and demonstrated for the first time to address above problems and extend the recording areal density beyond 1 Tbit/in2. The ECC grain of this novel medium consists of a magnetically hard region and a magnetically soft region. By tuning the coupling strength between the hard and soft regions in ECC grains, the switching field has been lowered tremendously while the media thermal stability is still maintained. This provides a pursuable way to use high anisotropy materials as writable media for future extremely high density magnetic recording.;In the first part of this thesis work, ECC medium was fabricated and prototyped using [Co/PdSiO]n as the hard layer and FeSiO as the soft layer. The key challenges in the fabrication of ECC media were addressed, such as in-plane exchange decoupling, columnar grain growth, interlayer coupling control, etc. The fundamental magnetic properties of ECC media were studied in detail. In the second part, ECC disk medium was fabricated using granular CoCrPt-SiO2 as both hard and soft layers. The recording performance and thermal stability of ECC media were evaluated and compared with conventional perpendicular magnetic recording media at disk-level, which gave the direct confirmation of the advantages of ECC media.