Effective reduction of the coercivity for Co${}_{72}$Pt${}_{28}$ thin film by exchange coupled Co${}_{81}$Ir${}_{19}$ soft layer with negative magnetocrystalline anisotropy

We report on the investigation of coercivity changes of the Co${}_{72}$Pt${}_{28}$/Co${}_{81}$Ir${}_{19}$ exchange-coupled composite (ECC) media with negative soft-layer (SL) magnetocrystalline anisotropy (MA) . Our results show that the hard-layer (HL) of our sample exhibits a columnar type microstructure with well isolated grains and the SL with hcp-structure grows on top of the HL with the same texture. Therefore, strong coupling of the two layers have been realized as evidenced by the magnetic characterization. Importantly, we observe a more effective reduction of the coercivity of the ECC media by using SLs with negative MA when compared to the use of SLs with positive or negligible MA. The experimental results are corroborated by theoretical calculations.