Search for magnetoelectric monopole response in Cr2O3 powder

The discovery of a monopole contribution to the overall magnetoelectric susceptibility of Cr${}_{2}$O${}_{3}$ sparked the search for a material with pure monopole response. Magnetoelectric powder samples are alternatives to magnetic topological insulators which, in practice, are not suitable candidates. Here, the authors experimentally and theoretically investigate the magnetoelectric susceptibility of Cr${}_{2}$O${}_{3}$ powder. Although electric and magnetic field cooling tunes the susceptibility, there is no field-cooling protocol that leads to a pure monopole response. These insights provide alternatives to realize effective magnetoelectric monopole media.