Magnetic properties of rare-earth-lean ThMn12-type (Nd,X)Fe11Ti (X: Y and Ce) compounds: A DFT study

Abstract

Due to the resource criticality of rare-earths (RE), an alternative to the well-known Nd2Fe14B magnets with a lower amount of critical elements is required. In this work, we performed density functional theory (DFT) calculations to investigate the influence of partial Nd substitution with more abundant elements (X: Y and Ce) in ThMn12-type (Nd,X)Fe11Ti compounds. In order to have a systematic understanding, the intrinsic magnetic properties such as the saturation magnetization (MS), Curie temperature (TC) and magnetocrystalline anisotropy energy (MAE), are screened starting from binaries RFe12 (R: Y, Ce and Nd). Ti is considered for the thermodynamic stabilization and different concentration of Ti is taken into account for ternaries RFe12−yTiy and quaternaries (Nd,X)Fe12−yTiy (0.5≤y≤1). In addition, the effect of nitrogenation is examined for each considered compounds. Special attention is given for the 4f-electrons treatment and their interaction with 3d-electrons. Each theoretical finding is compared with available experimental data. Since the experimental data is limited in the literature, we could only compare our results for ternaries and obtained reasonable agreement, which encourages us for the quaternary calculations. We have found promising magnetic properties for Nd-lean quaternaries that can be important for technological applications. In the case of (Nd,Y)Fe11Ti compound, |BH|max is found to be 508 kJ/m3, which is a higher value than Sm2Co17 magnets exhibit, and TC is calculated to be 595 K and it is higher than the TC of Nd2Fe14B. Similarly, |BH|max and TC is calculated to be 490 kJ/m3 and 593 K for (Nd,Ce)Fe11Ti magnet, respectively. For both rare-earth-lean quaternaries, our theoretical magnetic hardness factor κ yield to be 1.02, which qualifies them as good candidates for RE-lean permanent magnets.