Induced order and collective excitations in three-singlet quantum magnets

For even $f$-electron compounds (e.g., Pr, U) the ground state may be a nonmagnetic singlet, nevertheless magnetic order appears. The moments are induced simultaneously with ordering. This excitonic quantum magnetism is investigated by author within general three-singlet model. precursor soft excitons, transition temperature, and saturation moment derived. Furthermore, phase diagram possible first- second-order transitions critical behavior of exciton dispersions across obtained.