Exploring the negative thermal expansion and magnetocaloric effect in Fe2(Hf,Ti) Laves phase materials

Qi Shen*, Ivan Batashev, Fengqi Zhang, Hamutu Ojiyed, Iulian Dugulan, Niels van Dijk, Ekkes Brück

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)
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Abstract

The transition-metal based Laves phase materials represent an extended family of alloys with rich and fascinating physical properties. In this work, we have investigated the negative thermal expansion and magnetocaloric effect in arc-melted and melt-spun Fe2Hf1-xTix (x = 0.15, 0.27, 0.30, 0.33, 0.36, 0.40) alloys. For x = 0.30–0.40, two hexagonal phases with different compositions share the same P63/mmc lattice symmetry, but have slightly different lattice parameters. The saturation magnetization and Curie temperature both follow a decreasing trend with the average unit-cell volume. For Fe2Hf0.6Ti0.4 melt spinning improves the saturation magnetization from 48.7 to 59.6 Am2/kg and the magnetic entropy change from 0.46 to 0.54 J/kgK at a magnetic field change of 2 T. These enhanced values are attributed to an improved homogeneity caused by a suppression of phase segregation during rapid solidification. We have utilized neutron powder diffraction and Mössbauer spectroscopy to illustrate the correlation between the magnetic order and the negative thermal expansion in single-phase Fe2Hf0.85Ti0.15. The magnetic moments of Fe align below 400 K in the a-b plane and a moment change for the Fe atoms is responsible for the large volumetric coefficient of thermal expansion of −25 × 106 K1 over a wide temperature range of 300–400 K.

Original languageEnglish
Article number119149
JournalActa Materialia
Volume257
DOIs
Publication statusPublished - 2023

Keywords

  • Magnetocaloric effect
  • Negative thermal expansion
  • Neutron diffraction
  • Second-order phase transition

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