The Study On The Perpendicular Magnetic Anisotropy Of Co-based Alloy Thin Films

The ultrahigh density recording can be achieved by magnetic materials with larger magnetocrystalline anisotropy energy (MAE) to enhance the thermal stability of the single magnetic grain. Co-based alloy is always a research focus material for high-density magnetic recording media. According to systematic studies on the MAE of Co-based hcp alloy thin films, the MAE for Sm-Co, Co-W, and Co-Mo films is larger than Co-Cr-Pt films, which is the current of high density magnetic recording media. In this paper, a series of Co based thin films with magnetic perpendicular anisotropy (PMA) have been studied as follows:(1) We successfully utilized Ru (0002) textured film as underlayer for epitaxial growth of the highly (0001) textured SmCo5-xCux thin films with perpendicular anisotropy. Effects of Cu doping on the crystalline structure and magnetic properties of SmCo5-xCux thin films were investigated. With the increase of the Cu proportion, the Curie temperature (Tc) of SmCo5-xCux thin films is largely decreased. The ultra-high anisotropy energy and adjustable Tc indicate that Sm(Co,Cu)5magnetic film, which is thermally stable at room temperature and writable at an appropriate high temperature, could be a potential choice of heat assisted magnetic recording (HAMR) media materials.(2) Thermodynamic calculations based on Miedema’s semi-empirical model have been used to estimate the phase in Co-W binary alloy system. Based on the thermodynamic calculations results, a series of Co-W thin films were deposited on amorphous Ta underlayer with different tungsten concentrations. According to the X-ray diffraction results, the crystal structure of Co-W thin films is consistent well with that of thermodynamic calculations. Large MAE of Co-W thin films can be obtained with Ku over2.1×106erg/cm3after vacuum annealing. The perpendicular coercivity (Hc) of Co-W thin film reaches1147Oe. Therefore, the Co-W thin film is considered as a potential choice of high-density magnetic recording media materials.(3) We successfully prepared TbFeCo with PMA on Ta underlayer. We study Ta underlayer thickness dependence of PMA in TbFeCo films. The perpendicular Hc of the TbFeCo films significantly increases with the increasing Ta underlayer thickness which is due to the increase in the number of magnetic pinning sites. The oxidation of Tb atoms in the TbFeCo films can be effectively avoided by means of increasing Ta underlayer thickness, thereby reducing the Ms value of the TbFeCo films. While the Ta underlayer thickness is above4nm, the values of Mr/Ms are close to1.(4) We made a series of magnetic tunneling junction (MTJ) with hexagonal boron nitride (h-BN) spacer layer, and optimized the preparation condition, film morphology and texture. Finally, hcp Co/h-BN/hcp Co sandwich structure with high quality hcp Co/h-BN interface was obtained by rapid thermal annealing. It is a good foundation for the pattern of MTJ.