CdEr(2)Se(4): A New Erbium Spin Ice System in a Spinel Structure

we present a detailed study of the spinel CdEr(2)Se(4) and show it to be a new instance of spin ice, the first one in an erbium material and the first one in a spinel. Definitive experimental evidence comes from the temperature dependence of the magnetic entropy, which shows an excellent agreement with the predicted behavior for a spin ice state. Crystal field calculations demonstrate that the change in the local environment from that of the titanates completely alters the rare-earth anisotropy giving rise, in the case of Er(3+), to the required Ising anisotropy, when Er(2)Ti(2)O(7) behaves as an XY antiferromagnet. This finding opens up the possibility of new exotic ground states within the CdR(2)Se(4) and CdR(2)Se(4) families.