Magnetoresistance of perpendicularly magnetized tunnel junction using L1₀-CoNiPt with low saturation magnetization

Investigations of the structural and magnetic properties of thin Co _50-xNi_xPt₅₀ (x = 0, 10, 15, 37.5) films and fabrication of magnetic tunnel junctions (MTJs) using Co₅₀Pt ₅₀ and Co₃₅Ni₁₅Pt₅₀ electrodes were performed. X-ray diffraction analyses revealed that 20-nm-thick CoPt and CoNiPt films were epitaxially grown with (001)-orientation with an L1 ₀-chemical order parameter of 0.66-0.82. CoNiPt with various Ni contents magnetized perpendicularly; the saturation magnetization reduced to 157 emu/cm³ when the Ni content was increased to 37.5%. Magnetotransport measurements under a magnetic field applied perpendicular to the film plane revealed a tunnel magnetoresistance ratio of 10% and 1% at 10 K and 300 K, respectively, for MTJ using Co₃₅Ni₁₅Pt₅₀ electrodes.