MnGa (001)-Textured Film Fabricated on Thermally Oxidized Si Substrate for Application to Ion Beam Bit Patterned Media

Abstract

(001)-oriented MnGa films were grown on thermally oxidized Si substrates, and ion-beam patterned films using the MnGa grown on Si substrates were fabricated. The buffer layer of Cr (20 nm)/MgO (5 nm)/CrB (5 nm)/NiTa (25 nm) was used, and highly (001)-oriented and flat Cr buffer layer was obtained by high-temperature annealing of 800 °C. The large saturation magnetization $M_{\mathbf {s}}$ of 0.58 T, which is 74% of that of the epitaxial MnGa grown on MgO (001) substrate, was confirmed by growing the MnGa on the Cr buffer layer. As well as the large $M_{\mathbf {s}}$ , the MnGa on Si substrate exhibited a large perpendicular anisotropy. By using the (001)-oriented MnGa on Si substrate, ion-beam patterned structures whose pitch sizes down to 100 nm, corresponding to the areal density of 65 Gb/in2 were obtained. These results indicate that low-cost and high-density bit patterned media (BPM) were fabricated by the ion irradiation on MnGa grown on Si substrate. Furthermore, improvement of the crystal orientation of the buffer layer will be necessary to realize the MnGa BPM with the areal density of 1 Tb/in2 and more.