Magnetic pyrochlore oxides

Within the past $20\phantom{\rule{0.3em}{0ex}}\text{years}$ or so, there has occurred an explosion of interest in the magnetic behavior of pyrochlore oxides of the type ${{A}_{2}}^{3+}{{B}_{2}}^{4+}{\mathrm{O}}_{7}$, where $A$ is a rare-earth ion and $B$ is usually a transition metal. Both the $A$ and $B$ sites form a network of corner-sharing tetrahedra which is the quintessential framework for a geometrically frustrated magnet. In these systems the natural tendency to form long-range ordered ground states in accord with the third law of thermodynamics is frustrated, resulting in some novel short-range ordered alternatives, such as spin glasses, spin ices, and spin liquids, and much new physics. This article…