Structural phase transitions and magnetic characterization of Ba2GdNbO6 for low-temperature magnetocaloric refrigeration

DOI: 10.1021/acs.chemmater.5c01937

Authors: Fiamma Berardi (University of Cambridge) , Sian E. Dutton (University of Cambridge) , Liam A. V. Nagle-Cocco (University of Cambridge) , James M. A. Steele (University of Cambridge) , Xiaotian Zhang (University of Cambridge) , Cheng Liu (University of Cambridge) , Henry E. Fischer (Institut Laue-Langevin)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials

State: Published (Approved)
Published: October 2025
Diamond Proposal Number(s): 28349 , 34243

Abstract: Ba2GdNbO6 has previously been reported to adopt either monoclinic, tetragonal, or cubic symmetry at room temperature. Using high-resolution synchrotron X-ray diffraction, neutron diffraction and neutron pair distribution function analysis we find that the compound adopts a tetragonal I4/m double-perovskite structure at room temperature (with a weak, temperature-independent second-order Jahn–Teller distortion in the NbO6 octahedra) and undergoes a phase transition to a monoclinic P21/n symmetry upon cooling to 2.4 K. Only upon heating above room temperature to T ≈ 450 K does Ba2GdNbO6 reversibly transition to a cubic Fm3̅m symmetry. Magnetic susceptibility measurements indicate predominant paramagnetic behavior down to 1.8 K, with minimal ferromagnetic short-range correlations (θ = 0.20(5) K) and a small exchange interaction (J1 = −0.0032(8) K). At 2 K and 9 T, the compound exhibits a maximum magnetic entropy change of −ΔSm = 15.75 J K–1 mol–1 and an adiabatic temperature change of ΔTad = 21 K, making it a promising candidate for low-temperature magnetocaloric applications. Heat capacity measurements confirm a rigid crystal lattice (TD = 267(3) K) and a corresponding small lattice entropy contribution in the low-temperature regime, highlighting the potential of Ba2GdNbO6 for effective cooling capability in magnetocaloric devices at cryogenic temperatures. This study elucidates the structural and magnetic characteristics of Ba2GdNbO6 and attests to its promise for low-temperature magnetocaloric refrigeration.

Subject Areas: Materials, Chemistry, Physics


Instruments: I11-High Resolution Powder Diffraction

Other Facilities: D4c at ILL

Added On: 29/10/2025 15:23

Documents:
structural-phase-transitions-and-magnetic-characterization-of-ba2gdnbo6-for-low-temperature-magnetocaloric-refrigeration.pdf

Discipline Tags:

Physics Physical Chemistry Chemistry Magnetism Materials Science Inorganic Chemistry Perovskites Metallurgy

Technical Tags:

Diffraction X-ray Powder Diffraction