Abstract
This study presents the development of sustainable, flexible magnetochromic (MC) materials using Fe(3)O(4) (FO) and CoFe(2)O(4) (CFO) nanoparticles synthesized via environmentally friendly methods, along with NdFeB (ND) swarf from neodymium-iron-boron magnet waste. These nanoparticles are integrated with thermochromic (TC) pigments and poly-(vinyl alcohol) (PVA), forming a transparent, flexible polymer matrix. The use of green synthesis for FO and CFO minimizes hazardous chemicals and energy consumption, while the recycling of ND swarf addresses waste management and provides a cost-effective magnetic material. The resulting MC materials can be printed using eco-friendly techniques, offering a sustainable alternative to traditional sensing materials. The devices demonstrate fast color changes between red and gray within 3-5 s under an alternating magnetic field (200 Oe, 100 kHz), making them ideal for applications in flexible electronics, smart textiles, and sensors. With a focus on environmental responsibility, these materials meet the increasing demand for sustainable technologies in advanced optical sensing systems.