- 學位論文
微粒狀序化鐵鉑合金參硼以及參硼和碳之薄膜應用於能量輔助磁記錄
Granular L10 FePt:B and FePt:B,C for Energy Assisting Magnetic Recording
摘要
序化鐵鉑合金具有極高的磁異向性 (Ku~107erg/cc)，在輔以能量寫入的方式下，被認為有機會打破磁記錄中的三元拮抗現象，進而大幅提高記錄密度。作為紀錄層的序化鐵鉑合金不但必需具有高序化度和單一鐵鉑(001)織構，近年來，為了達到更小的粒狀尺寸以及降低粒狀鐵鉑合金之間的磁交互作用力，多種分離體一一被嘗試添加在鐵鉑合金之中。在目前已知分離體中，硼具有低溫的高擴散性以及相近於序化鐵鉑的表面能，因此被推論能具有較小的序化鐵鉑尺寸以及柱狀結構。 首先，我們製備了序化粒狀鐵鉑合金參雜硼的磁性薄膜，並發現絕大多數的硼會佔據粒狀鐵鉑的晶界，切割鐵鉑合金使其尺寸大幅的下降，卻有部分的硼會佔據鐵鉑合金的間隙位置，阻礙鐵的擴散，甚至形成微量的鐵硼相，進而造成序化反應的能障提高。由於碳，在目前已知的分離體中，具有對於鐵鉑合金序化度的傷害較小，且不易和硼反應的特性，我們接著製備了序化粒狀鐵鉑合金同時參雜硼和碳的磁性薄膜。藉由改變製成方式來降低硼佔據鐵鉑間隙位置的機率，並同時利用碳作為分離體的特性，成功製備出高序化度、垂直矯頑場2.5 T、單一鐵鉑(001)織構以及粒狀尺寸6~8 nm的磁性薄膜。
並列摘要
Media trilemma has been the barrier for increasing the recording density of HDD for years. To break through the media trilemma in HDD, the ideal of granular L10 FePt for energy assisting magnetic recording was proposed and several requirements for granular L10 FePt must be achieved such as large perpendicular coercivity (>1.8T), small granular size, FePt (001) prefer orientation, narrow grain size distribution, narrow switch field distribution and columnar growth. Among all segregants, the grain size of FePt:B presented the smallest grain size and the surface energy of boron (~2.3kJ/m2) is the closet to it of FePt (~2.5kJ/m2) which means the potential to promote columnar growth. We first fabricated granular FePt:B and studied the effect of adding boron into FePt. It was found that boron would significantly hinder FePt order-disorder transition and thus contributed a rather low perpendicular coercivity. To solve this problem, the post-annealing processes were carried out to promote FePt order-disorder transition and the behavior of boron during FePt order-disorder transition was studied. However it turned out to be a dilemma between granular structure and magneto-crystalline anisotropy. According to recent work, carbon was considered to be the one that would not hinder the FePt order-disorder transition heavily nor degrade the crystalline of FePt (001) and (002). Therefore, the coercivity of granular L10 FePt:C was higher than it in other segregants. The ideal of multi-segregant of granular FePt:B,C was then proposed to take the advantages of both boron and carbon. We first fabricated granular L10 FePt:C as an ordered seed layer and then capping boron onto FePt:C. By post annealing, we successfully demonstrated multi-segregant of granular FePt:B,C.