Effect of Amorphous/Crystalline Material Doping on the Microstructure and Magnetic Properties of FePt Thin Films

The effects of various doping materials (amorphous phases: TiO₂, SiO₂, MgO, and C and crystalline phases: HfO₂ and ZrO₂) on the microstructure and magnetic properties of FePt thin films have been investigated. It is found that FePt films with amorphous doping materials especially MgO and C have better (001) texture and grain isolation than doping with crystalline materials. Nevertheless, doping with crystalline materials, FePt films were preferred to form columnar structures with a larger aspect ratio compared with semi-spherical grain shape for amorphous doping materials. Moreover, all the FePt-X films exhibit better perpendicular anisotropy except for FePt-ZrO₂ films due to some FePt (200) textured films epitaxial grown directly on tetragonal (002) textured ZrO₂. For crystalline materials doping, the (001) texture and perpendicular anisotropy could be improved by tuning crystalline oxide materials with appropriate lattice structure, which may offer a method for application in FePt in heat-assisted magnetic recording media.

I. Introduction

The data storage capacity of hard disk drives needs to be increased to meet the huge demand of storing exponentially increasing digital information. FePt-based heat-assisted magnetic recording media have drawn a lot of attention due to their ability to extend the areal density from 1 up to 5 Tb/in² [1]–[4]. For practical applications, it is imperative to fabricate FePt films with good (001) texture, large magnetocrystalline anisotropy, and small grain size with a narrow size distribution. In order to achieve this goal, a lot of progress has been made in the fabrication of granular FePt thin films by selecting various materials to incorporate into the FePt films to isolate and reduce the grain size [5]–[12]. These segregants should not react with or dissolve in FePt during the high-temperature processing of the film growth and also not be corrosive, radioactive, or hazardous. Until now, the segregants reported in this paper are almost amorphous. The crystalline phases used as segregrants were rarely investigated. Moreover, the different evolution of microstructures and magnetic properties of the FePt films after doping with amorphous and crystalline materials need to be clarified. For this purpose, the objective of this paper is to study the effect of doping various segregants (amorphous phases: TiO₂, SiO₂, MgO, and C and crystalline phases: HfO₂ and ZrO₂) doping on the microstructure and magnetic properties of FePt thin films.