Pyrochlore magnets have been a playground for exotic magnetic ground states as many of these are characterized by quantum S=1/2 degrees of freedom decorating a three dimensional network of corner-sharing tetrahedra – one of the canonical crystalline architectures supporting geometrical frustration in materials. Recently, we and others have been studying Ce-based pyrochlores, including Ce2Zr2O7 and Ce2Sn2O7, whose S=1/2 degrees of freedom possess both a dipolar and an octupolar character, by virtue of the symmetry properties of Ce3+’s ground state crystal field doublet. In principle, this allows a ground state phase diagram for such materials that includes both ordered and quantum disordered ground states each of which can have either dipolar character or octupolar character. I will discuss how this exotic dipole-octupole S=1/2 degree of freedom arises in the J=5/2 Ce3+ ion in this environment. I will then review our recent experimental work, based mainly of low temperature thermodynamics and neutron scattering, that makes the case that Ce2Zr2O7 displays a disordered quantum spin ice ground state, while Ce2Sn2O7 is a candidate for an ordered All In – All Out Neel state.
Mc Master University, Canada, Ontario