Bulk Modulus of φ-Nd₂Fe₁₄B and NdH₂ phases revealed by in-situ synchrotron XRD under high-pressure conditions

The mechanical behavior of Nd₂Fe₁₄B magnets under pressures exceeding 20GPa is unexplored due to a lack of experimental data. Here, we report the high-pressure compressibility of Nd₂Fe₁₄B and NdH₂ powders, investigated via in situ synchrotron X-ray diffraction up to 40GPa. While both phases show a similar bulk modulus (~67GPa), their pressure derivatives differ drastically, Nd₂Fe₁₄B exhibits a high K′ of 10.1, whereas NdH₂ shows a value of 4.0. This contrast reveals a progressive stiffening in the anisotropic Nd₂Fe₁₄B lattice, compared to the near-ideal elastic response of NdH₂. Furthermore, the development of a pronounced texture under pressure, evidenced by the enhanced intensity of specific (hkl) planes, indicates preferential crystal reorientation. These results uncover the distinct high-pressure accommodation mechanisms in Nd₂Fe₁₄B-based magnets, providing critical insights for their design and stability under extreme conditions. • Bulk moduli of φ-Nd₂Fe₁₄B and NdH₂ phases measured up to 40 GPa. • High-pressure XRD reveals anisotropic lattice compression in Nd₂Fe₁₄B. • NdH₂ phase displays quasi-ideal elastic response under compression. • Strong stiffening of Nd₂Fe₁₄B confirmed by high pressure derivative K′ ≈ 10. • Results support mechanical resilience of NdFeB-based magnets under stress.