Time-Reversal Symmetry Breaking and Consequent Physical Responses Induced by All-In-All-Out Type Magnetic Order on the Pyrochlore Lattice

The physical properties of pyrochlore compounds with the all-in-all-out type arrangement of magnetic moments are discussed. The magnetic order can be regarded as a ferroic order of magnetic octupole moments, which does not give rise to macroscopic magnetization but breaks the time-reversal symmetry. As a result of the time-reversal symmetry breaking, the magnetostriction, magnetocapacitance, Voigt magnetooptic effect, and magnetic susceptibility are expected to have a term linear to the external magnetic field. Another striking consequence of the magnetic order is the presence of spontaneous magnetization and scalar spin chirality on the most stable {111} surfaces. This may pave the way for unique surface magnetotransport phenomena.