Perpendicular magnetic anisotropy enhancement and thermal stability study in Co/Pt multilayers with MgO/Pt interface

The Co/Pt multilayers with Pt and MgO/Pt underlayer were prepared by magnetron sputtering and the perpendicular magnetic anisotropy(PMA) of the multilayers were researched by the means of Anomalous Hall effect (AHE). The annealing effect study of Pt(1.0)/[Co(0.4)/Pt(0.8)](3)(unit: nm) shows that the sample has pretty good thermal stability but the coercivity(H-C) has little change. The experimental results show that the PMA and Hc of Co/Pt multilayers was improved greatly by the additional scattering of electrons induce from the amorphous insulator-metal interface of MgO-Pt. When MgO layer thickness(t(MgO)) is 4nm, the Hall resistance (R-Hall) of MgO(4)/Pt(1.0)/[Co(0.4)/Pt(0.8)](3) multilayer has a maximum value of 2.11 which is increased by 16%. Furthermore the Hc increases to 172Oe which is more than 1.5times to Pt(1.0)/[Co(0.4)/Pt(0.8)](3) multilaye and the Hc meets the maximum value of 204Oe when t(MgO) is 2 nm. Annealing effects of MgO(4)/Pt(2)/Co(0.2)/Ni(0.4)/Co(0.2)/Pt(2) show that it has good thermal stability and the Hc reaches its maximum value of 438Oe at annealing temperature(T-A) of 300 degrees C. The multilayer begins to lose the PMA property at higher T-A. The Hysteresis loop of MgO(4)/Pt(1.0)/[Co(0.4)/Pt(0.8)](3) multilayer annealed at 300 degrees C was tested and the anisotropy constant(K-eff) was obtained as 8.9 x 10(6) erg/cm(3), which is about 4.45times the Pt(1.0)/ [Co(0.4)/Pt(0.8)](3) multilayer. The PMA of Co/Pt multilayers is greatly enhanced by MgO/Pt interface and annealing treatment.