Resolution of the nature of the ferromagnetic state in ternaryEuRh3B2: Giant Mössbauer quadrupole splitting

Determination of the magnetic properties of nearly stoichiometric ${\mathrm{EuRh}}_3$B2 on macroscopic and microscopic levels reveals that its ferromagnetism originates from the ordering of the spins of divalent Eu perpendicular to the hexagonal c aixs. This finding contradicts previous reports of Rh 4d-band itinerant-electron ferromagnetism and a nonmagnetic trivalent Eu state. The value of the ${}_{}{}^{151}{}_{}{}^{}\mathrm{Eu}$ Mössbauer quadrupole splitting, ${\mathrm{e}}^2$qQ=48±1 mm/s, is by far the largest ever reported for any Eu system and results from the extremely short Eu-Eu separation.