Fabrication\nof Ultrafine L1<sub>0</sub>‑FePt-Based\nMagnetic Patterns Enabled by Single-Step Nanoimprint-Assisted Block\nCopolymer Self-Assembly

The bit islands in magnetic patterns play a crucial role\nin advancing\nmagnetic recording density, but the trade-off issues between miniaturization\nand scalable production are still challenging. Here we present a two-in-one\ntechnique of nanoimprint lithography (NIL)-assisted self-assembly\nusing a specially engineered FePt-containing block copolymer (BCP),\noffering a simple one-step fabrication for L1<sub>0</sub>-FePt bit-patterned\nmedia with high throughput. This method combines top-down NIL with\nbottom-up self-assembly to precisely control the ultrafine magnetic\nbits in the nanoscale patterns. The FePt-derived BCPs, designed with\nan equal atomic ratio of Fe and Pt, ensure the preparation of homogeneously\ndispersed L1<sub>0</sub>-FePt nanoparticles (NPs). Subsequent BCP\npyrolysis results in NPs with enhanced magnetic properties, significantly\nadvancing high-density data storage devices. This strategy offers\na novel approach to drive the innovative creation of ordered magnetic\nmetal alloy NPs arrays for practical applications.