Geochemical tracing of Nd magnets – a possible future tool to improve sustainable sourcing of critical raw materials?

Raw material supply chains are intricate and complex systems that often suffer from a lack of transparency. To enhance sustainability in mineral supply, there is an urgent need to rectify this transparency deficit. Traceability, which involves tracking a product through different stages of production, transformation, and commercialization, from its origin to its end-of-life, including potential recycling, could be a crucial facilitator for increased transparency. Nd magnets (also known as NdFeB magnet) are the strongest permanent magnet type known and serve as critical components in green technologies like windmill turbines and electric motors for vehicles. While Nd magnets offer numerous advantages, their production involves the use of rare earth elements (REE), critical raw materials that lack supply chain transparency, standards, and certification schemes regarding environmental and social impacts, and governance. The objective of this study is to investigate whether there are distinct chemical characteristics associated with Nd magnets and to determine the feasibility of establishing a correlation between a magnet and unidentified information, potentially linking it to a plausible source. Nd magnets have been systematically collected for the purpose of tracing their material origins. Two distinct categories of Nd magnets were assessed for this investigation. The first category comprises novel magnets with documented production years (ranging from 1999 to 2023) and varying grades marked by different Nd contents. The second category consists of magnet scraps lacking specific information. Our study employed a comprehensive approach, incorporating automated quantitative mineralogy (AQM), Scanning Electron Microscope spectroscopy element mapping (SEM-EDS) to examine microtextures and major element content, and LA-ICP-MS analyses for trace elements and Nd isotopes. Analyzing these magnets revealed noticeable compositional distinctions among samples, both in terms of manufacturing sources and production years. Four distinct groups of trace elements were identified in the novel magnets, aiding in the differentiation of various production year groups. These groups include Ti, Cr, Se, La, Cr, Nd, Gd, Yb (Group 1), B, Eu, Tb (Group 2), Al, As, Ge, Pr, Sm, Dy, Tm (Group 3), and Mn, Ho (Group 4). Nd isotope analyses indicated a broad present-day epsilon Nd values, ranging from -30 to -7, with some degree of inter-sample overlaps. This extensive range appears to surpass the typical coverage of REE deposits. Higher values suggest the potential incorporation of REEs from South China ion-absorption deposits, while lower values hint at the involvement of REEs from Olympic Dam (Australia) and/or Mountain Pass (US). These preliminary findings contribute with valuable insights into the diverse origins and compositions of Nd magnets, suggesting that geochemical fingerprinting could emerge as a pivotal traceability tool for assessing the origin of Nd magnets in the future.