Hydrogen-Induced Order–Disorder Effects in FePd3

Binary intermetallic compounds, such as FePd3, attract interests due to their physical, magnetic and catalytic properties. For a better understanding of hydrogenation properties, both ordered FePd3 disordered Fe0.25Pd0.75 are studied by several in situ methods, thermal analysis, X-ray powder diffraction neutron diffraction, at moderate hydrogen pressures up 8.0 MPa. absorbs small amounts room temperature follows Sieverts’ law solubility metals. [Pd6] octahedral voids filled 4.7(9)% statistical manner 8.00(2) MPa, yielding the hydride FePd3H0.047(9). This is accompanied decreasing long-range order Fe Pd atoms (site occupancy factor Wyckoff position 1a from 0.875(3) 0.794(4)). trend also observed during heating, while moment decreases Curie 495(8) K. The dependences moments iron under isobaric conditions (p(D2) = 8.2(2) MPa) consistent with 3D Ising or Heisenberg model (critical parameter β 0.28(5)). atomic content show complex interplay.