Structure-dependent polar kerr rotation in CoPt/AlN layered films

Polar magneto-optical Kerr effect (P-MOKE) has found extensive applications in magnetic storage, magneto-optical sensors, and spintronic devices. In this study, we investigate the P-MOKE response of multilayer films composed of cobalt platinum (CoPt) alloys and aluminum nitride (AlN), fabricated via DC magnetron sputtering. We observe a magnetization-alignment-dependent behavior, with interference effects contributing to the overall Kerr rotation. Notably, a significant enhancement in P-MOKE is achieved in the substrate/AlN(20 nm)/CoPt(3 nm)/AlN(15 nm) structure, which is attributed to the interference effects induced by the AlN dielectric layer. Furthermore, a distinctive jump in the Kerr rotation hysteresis loop is observed in the substrate/AlN(20 nm)/CoPt(3 nm)/AlN(15 nm)/CoPt(3 nm) configuration, due to the antiparallel alignment of the magnetization between top and bottom CoPt layers. AlN-thickness-dependent behaviors in the P-MOKE signal have also been found in the CoPt/AlN/CoPt trilayer structure. The effective refractive index method and transfer matrix method are employed to quantitatively explain the anomalous Kerr rotation. This study highlights the exceptional sensitivity of P-MOKE to both magnetization configuration and multilayer structure, underscoring its potential for advanced magneto-optical applications.