Structural, Magnetic, and Electric Properties of Pt/Co/Au/Cr2O3/Pt Thin Film with Cr2O3 Layer below 25 nm

Perpendicular exchange bias using magnetoelectric Cr 2 O 3 has an electric-field triggered switching ability, and the thickness limit of the Cr 2 O 3 layer for inducing this bias is a topic of research. In this paper, we investigated the structural, magnetic, and electric properties of Pt/Co/Au/Cr 2 O 3 /Pt thin films with a Cr 2 O 3 layer in the thickness range of 5.7 to 25 nm. By using a magnetron sputtering method, a well-crystallized Cr 2 O 3 (0001) layer was formed in 5.7-nm-thick Cr 2 O 3 . All studied films showed perpendicular magnetic anisotropy. The uniaxial magnetic anisotropy energy density increased as the Cr 2 O 3 thickness decreased, and 810±90 kJ/m 3 was obtained for the film with 5.7-nm-thick Cr 2 O 3 . Perpendicular exchange bias was evaluated above 80 K, and an exchange anisotropy energy density of 0.30 mJ/m 2 was observed for the film with a 25-nm-thick Cr 2 O 3 at 80 K. The exchange bias could not be observed below 18 nm. Instead, coercivity enhancement, which yields the exchange bias by precisely controlling interfacial exchange coupling, was observed. The electric resistivity was about 5  10 5  ·m for the 5.7-nm-thick Cr 2 O 3 layer, which is sufficiently high for magnetoelectric applications.