Effects of ion irradiation on epitaxial Cu/Ni/Cu(001) with perpendicular magnetic anisotropy

Epitaxial fcc Cu/Ni(t)/Cu(001) structures (t=20,30,60,90 A) possessing perpendicular magnetic anisotropy were irradiated by 1 MeV C+ with a dose of 2×1016 ions/cm2. The spin reorientation transitions from perpendicular to in-plane magnetization occurred after ion irradiation. X-ray diffraction measurements showed that the crystal structures were conserved, the grain sizes of Cu in the Cu/Ni(60, 90 A)/Cu(001) films increased by 38%, and the strain in the Ni layer was relaxed after irradiation when compared to the as-deposited samples. It is concluded that the spin reorientation transition is caused by the relaxation of the strain in Ni layer, which is initiated by ion irradiation.