Magnetically driven giant negative thermal expansion covering room temperature in Hf0.875Ta0·125Fe2

L. V. B. Diop (1) , O. Isnard (2)

1 IJL - Institut Jean Lamour
2 NEEL - MRS - Matériaux, Rayonnements, Structure

Neutron diffraction is used to reveal the origin of the unusual thermal expansion properties of the itinerant-electron system Hf0.875Ta0.125Fe2. Hf0.875Ta0.125Fe2 shows temperature-induced magnetic transitions from ferromagnetic (FM) to antiferromagnetic (AFM) order and then to the paramagnetic (PM) state upon heating. The FM-AFM transition proceeds in a stepwise fashion, as a first-order phase transition, and is accompanied by an extremely anisotropic lattice collapse. The unit cell volume shrinks abruptly, but only in the basal plane; the dimension along the c-axis varies almost continuously. Hf0.875Ta0.125Fe2 exhibits a 0.37 % spontaneous volume contraction across the FM-AFM transition, where a giant negative thermal expansion (NTE), with a volumetric thermal expansion coefficient-74×10-6 K-1 , is observed over a temperature interval of ΔT~50 K around room temperature.

Mots clés: Intermetallic compound; Neutron powder diffraction; Negative thermal expansion; Magnetoelastic transition *

Domaines: Physique [physics]; Matière Condensée [cond-mat]; Science des matériaux [cond-mat.mtrl-sci]; Cristallographie; Matériaux

L. V. B. Diop, O. Isnard. Magnetically driven giant negative thermal expansion covering room temperature in Hf0.875Ta0·125Fe2. Solid State Communications, 2020, 320, pp.114021. ⟨10.1016/j.ssc.2020.114021⟩. ⟨hal-02920018⟩