Structure, magnetism and low thermal expansion in Tb_1-xEr_xCo₂Mn_y intermetallic compounds

Abstract

Here, we obtained a series of controllable thermal expansion alloys Tb_1-xEr_xCo₂Mn_y (x = 0-0.5, y = 0-0.4) by incorporating double rare earth doping and introducing non-stoichiometric Mn content. By varying the amount of Er or Mn, a low thermal expansion (LTE) is achieved in Tb_0.6Er_0.4Co₂Mn_0.1 (TECM, α₁ = 1.23 × 10^-6 K^-1, 125~236 K). The macroscopic linear expansion and magnetic properties reveal that anomalous thermal expansion is closely related to the magnetic phase transition. Synchrotron X-ray powder diffraction results show that TECM is a cubic phase (space group: Fd-3m) at high temperatures, and a structural transition to a rhombohedral phase (space group: R-3m) occurs as temperature decreases. The negative thermal expansion c-axis compensates for the normal positive thermal expansion of the basal plane, resulting in the volumetric LTE. This study provides a new metallic and magnetic ZTE material.

Keywords

Zero thermal expansion / crystal structure / microstructure / magnetism

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