High pressure synthesis and characterization of the pyrochlore Dy₂Pt₂O₇: A new spin ice material

The cubic pyrochlore Dy₂Pt₂O₇ was synthesized under 4 GPa and 1000℃ and its magnetic and thermodynamic properties were characterized by DC and AC magnetic susceptibility and specific heat down to 0.1 K. We found that Dy₂Pt₂O₇ does not form long-range magnetic order, but displays characteristics of canonical spin ice such as Dy₂Ti₂O₇, including (1) a large effective moment 9.64 μ_B close to the theoretical value and a small positive Curie-Weiss temperature θ_CW=+0.77 K signaling a dominant ferromagnetic interaction among the Ising spins; (2) a saturation moment ～4.5 μ_B being half of the total moment due to the local <111> Ising anisotropy; (3) thermally activated spin relaxation behaviors in the low (～1 K) and high (～20 K) temperature regions with different energy barriers and characteristic relaxation time; and most importantly, (4) the presence of a residual entropy close to Pauling's estimation for water ice.