Magnetothermodynamics of the Ising antiferromagnet Dy2 Ge2 O7

We report systematic low-temperature measurements of the dc magnetization, ac susceptibility, and heat capacity of dysprosium pyrogermanate (Dy2 Ge2 O7) single crystal and powder samples. Our results confirm that Dy2 Ge2 O7 is an anisotropic antiferromagnet. The isothermal field dependent magnetization and the integrated magnetic entropy both indicate that the Dy3+ ions behave as Ising-like spins, analogous to those in the pyrochlore spin ice materials. Both single-spin and collective spin-relaxation phenomena appear to lead to spin freezing in this material, again in analogy to observations in the spin ice materials, suggesting that such phenomena may be generic to a broader class of magnetic materials.