Observation of long range magnetic ordering in pyrohafnate Nd2Hf2O7: A neutron diffraction study

الأصل · EN

We have investigated the physical properties of a pyrochlore hafnate Nd2Hf2O7 using ac magnetic susceptibility χₐc(T), dc magnetic susceptibility χ(T), isothermal magnetization M(H) and heat capacity Cₚ(T) measurements, and determined the magnetic ground state by neutron powder diffraction study. An upturn is observed below 6 K in Cₚ(T)/T, however both Cₚ(T) and χ(T) do not show any clear anomaly down to 2 K. The χₐc(T) shows a well pronounced anomaly indicating an antiferromagnetic transition at Tₙ = 0.55 K. The long range antiferromagnetic ordering is confirmed by neutron diffraction. The refinement of neutron diffraction pattern reveals an all-in/all-out antiferromagnetic structure, where for successive tetrahedra, the four Nd3+ magnetic moments point alternatively all-into or all-out-of the tetrahedron, with an ordering wavevector k = (0, 0, 0) and an ordered state magnetic moment of m = 0.62(1) μB/Nd at 0.1 K. The ordered moment is strongly reduced reflecting strong quantum fluctuations in ordered state.