Micro-Structure and Magnetic Properties of Perpendicular Magnetized Co-CoO Sputtered Films

The electrical resistivity of reactive RF sputtered Co-CoO films increases and the temperature coefficient of resistivity decreases with the formation of CoO. For films with a saturation magnetization (M
s
) of more than 670 emu/cm
³
, the resistivity decreases irreversibly above 370 K by deoxidization. For films with an M
s
of less than 470 emu/cm
³
, the resistivity increases irreversibly above 420 K. After the irreversible increase in resistivity, the coercivity (H
c
) and squareness ratio of the hysteresis loop perpendicular to the film plane increase, and the H
c
parallel to the film plane decreases.