Semihard magnetic properties of TiFe2.5 iron-rich Laves phase and the effect of 4d- and 5d-element-substitutions for Ti

• Published in: Journal of magnetism and magnetic materials Vol. 583; p. 171080
• Main Authors: Gabay, A.M., Han, Chaoya, Ni, Chaoying, Hadjipanayis, G.C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01-10-2023; Elsevier
• Subjects: Laves phase; Magnetic anisotropy; MATERIALS SCIENCE; Rare-earth-free magnets; Spin-orbit coupling; Rare-earth-free magnets; Spin–orbit coupling; Magnetic anisotropy; Laves phase
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2023.171080

•Magnetic anisotropy of Fe-rich TiFe2.5 Laves phase is uniaxial, but it is weak.•Nb, Mo, Ta, W increase the anisotropy field only below room temperature.•Zr, Hf increase the Curie temperature and lead to a spin reorientation below 200 K.•Maximum coercivity induced via high-energy milling is 2.9% of the anisotropy field.
Rare-earth-free compounds exhibiting modest intrinsic hard magnetic properties may still yield viable permanent magnets if their constituent elements are abundant and inexpensive, and the properties are at least comparable to those of the hard ferrites. In this study, one such compound, the off-stoichiometric TiFe2.5 Laves phase with the hexagonal C14 crystal structure, was found to exhibit – in addition to the already known room-temperature ferromagnetism – a uniaxial, albeit weak, magnetic anisotropy. With a Curie temperature of 422 K, saturation magnetization of 55.3 Am2/kg and magnetic hardness parameter of 0.97 this semihard compound is just below the threshold for being of interest for the development into permanent magnets. Replacing a small fraction of Ti with the 4d Nb and Mo or with the 5d Ta or W increases the anisotropy field, but only below room temperature. Replacing Ti with Zr or Hf increases the Curie temperature and leads to a spin reorientation below 200 K. All these substitutions, as well as combined (Zr,W) and (Nb,W) substitutions, fail to improve the room-temperature intrinsic hard magnetic properties of the Fe-rich Laves phase. Furthermore, an attempt to develop a room-temperature coercivity through high-energy ball-milling yielded a value of 0.026 T, an unusually small 2.9% fraction of the anisotropy field. Defects inherent in the C14 crystal lattice may be responsible for the underperformance.