TbFeCo交換耦合雙層碟片用於熱磁寫入與磁通量讀出之磁性質與記錄特性

Abstract

磁光碟片的記錄密度與受限於記號大小。當記號小於雷射光之光學繞射極限時，記號將無法清楚的被解析，讀出訊號會變差。此外，對於目前商用磁光碟片而言，當記號小於 0.5μm 時，其載波雜訊比也不足夠用於讀取上。為了提升碟片密度並維持適當之讀取訊號，利用 TbFeCo 交換耦合雙層碟片（ECDL）並結合目前磁光碟機所使用之熱磁寫入法與硬碟機所使用之磁通量偵測法的複合式記錄機制便被提出使用。TbFeCo 雙層耦合交換碟片可同時具有下面雙重磁性質：高磁化量用於磁通量偵測與高矯頑磁力用於維持小記錄磁矩之穩定。 利用 ECDL 碟片同時具有高磁化量與高矯頑磁力之特性，並使用玻璃基板製作成碟片，爾後用動態光碟測試機做寫入測試。當使用表面入射、記錄層為RE-rich 讀出層為 TM-rich 之 ECDL 碟片結構以及適當之寫入參數，可順利在碟片寫上約 0.33μm 大小之記號。雖然尚未有巨磁阻磁頭做磁通量讀取測試，但利用磁力顯微鏡已可清楚的觀察到 0.33μm 記號之磁矩磁相位圖形。實驗結果發現，使用記錄層為RE-rich 讀出層為 TM-rich 之 ECDL 碟片結構與表面入射寫入方式可適當的驗證熱磁寫入與磁通量偵測法，對於記錄密度將有明顯的提升。

The recording density of magneto-optical (MO) disk is determined by the recorded mark size. When the mark size is smaller than the optical diffraction limit, the readout signal decreased severely. Furthermore, when the mark size is smaller than 0.5μm on current commercial MO disk, the carrier to noise ratio (CNR) becomes inadequate for reading. In order to increase the recording density of MO disk, yet maintain adequate readout signal, the mechanism combining thermo-magnetic writing on current MO disk and magnetic flux detection readout of hard disk drive is proposed by using TbFeCo-based exchange-coupled dual layer (ECDL) disk. The ECDL disk was shown to possess both high magnetization (Mr) for magnetic flux detection and high coercivity (Hc) for keeping the small recorded marks stable. By using the ECDL media, the glass substrate media having both high Mr and Hc were fabricated for thermo-writing by using the dynamic optical disk tester. With surface incidence and RE-TM (recording layer is RE-rich, readout layer is TM-rich) ECDL structure, the mark size about 0.33μm was recorded on the disk by proper writing parameters. Though the giant magneto-resistive head to detect magnetic flux is not available, the recorded domain image of 0.33μm was observed clearly by the magnetic force microscope (MFM). Experimental results revealed that RE-TM ECDL disk structure and surface incidence writing process are adequate for thermo-writing and magnetic flux detection to increase the recording density.