Crystal-Field Origin of the Giant Magnetocrystalline Anisotropy of PrRu2Si2

PrRu2Si2 shows ferromagnetism below 14 K with the ordered moment of 2.7μB.It exhibits an enormous magnetic anisotropy at 4.2 K with the anisotropy field of about 400 T. We have attrributed the magnetism of PrRu2 Si2 to the Pr 3 + ions.Thus we performed calculations of the fine electronic structure of the Pr 3+ ion in the tetragonal symmetry, relevant to PrRu2Si2, taking into account crystal-field and inter-site exchange interactions.Our calculations reproduce well the zero-temperature moment, the single-crystalline magnetization curves, and giant anisotropy field as 400 T. The magnetocrystalline-anisotropy energy K1 of 59 J/cm 3 is the largest known anisotropy -the anisotropy energy of the Nd 2 Fe 14 Β supermagnet amounts to 12.5 J/cm 3 only.Unfortunately, this giant anisotropy is confined to low temperatures only which prohibits its technical applications in the permanent-magnet industry.