Fabrication of L11 type Co-Pt ordered alloy films by sputter deposition

Abstract

L 1 1 type Co-Pt ordered alloy films with a large uniaxial magnetic anisotropy, Ku, of the order of 107erg∕cm3 were successfully fabricated at relatively low substrate temperatures of 270–390°C using ultrahigh vacuum sputter film deposition. L11 type ordered Co-Pt films, with the ⟨111⟩ direction (easy axis of magnetization) perpendicular to the film plane, were fabricated on MgO(111) single crystal substrates and glass disks. The ordered structure was formed in a wide Pt content region of 40–75at.%, and Ku showed a maximum at around 50at.% Pt content. The values of the order parameter S and Ku for L11 type Co50Pt50 films increased as the substrate temperature Ts, increased. Ku reached about 3.7×107erg∕cm3 (S=0.54) at Ts=360°C for the single crystal films deposited on MgO(111) substrates, indicating a potential increase in Ku by enhancing the ordering. The values of Ku for polycrystalline films deposited on glass disks were smaller than those for the single crystal films on MgO(111) substrates, however, Ku reached 1.9×107erg∕cm3 at Ts=360°C. The experimental results demonstrate the potential of L11 type Co50Pt50 films for use in data storage applications, because of their very high Ku, comparable to L10 type Fe50Pt50 films, the relatively low fabrication temperature, and good controllability of the grain orientation.

Effect of additional elements on compositional modulated atomic layered structure of hexagonal Co80Pt20 alloy films with superlattice diffraction

“…3 shows M s and K u for (Co 80 Pt 20 ) 100-x M x (M: Si, Cr, Ti, Zr, W, x: 0-10 at.%) sputtered alloy films. The addition of any metal element until 10 at.% to CoPt alloy, will decrease M s gradually from 1150 to around 800 emu/cm 3 . This gradual reduction of M s indicates that all the added metal elements form solid solutions with CoPt alloy.…”

“…[1][2][3][4][5][6] In practice, for current perpendicular recording medium, granular film which consists of CoPt alloy and oxide has been widely used. To increase thermal stability of the recording medium, the enhancement of K u is indispensable.…”

“…In this study it is found that the addition of Cr or W element to Co 80 Pt 20 alloy film shows less deterioration of hcp stacking structure and compositionally modulated atomic layer stacking structure as compared to Si or Zr or Ti with K u of around 1.4 or 1.0×10 7 erg/cm 3 at 5 at.% addition. Furthermore, for O 2 addition of O 2 ≥ 5.0×10 −3 Pa to CoPt alloy, compositionally modulated atomic layer stacking structure will be deteriorated with enhancement of formation of hcp stacking structure which leads higher K u of 1.0×10 7 erg/cm 3 …”

Structure analysis of CoPt alloy film with metastable ordered phases ofL11andBhformed on Ru(0001) underlayer

“…An L1 1 CoPt film with the longrange order degree (S) of 0.33 is reported to show K u of 1.7×10 7 erg/cm 3 along the direction normal to the closepacked plane [5]. A theoretical calculation suggests that the K u value increases up to 10 8 erg/cm 3 with increasing the S value [9].…”

“…Formation of metastable L1 1 ordered phase has been recognized for CoPt alloy films deposited on MgO(111) substrates around 300 °C [4][5][6][7][8]. The L1 1 structure consists of alternate stacking of close-packed planes of Co and Pt, as shown in figure 1(a).…”