Pressure-induced transition of the sublattice magnetization in EuCo2P2:: Change from local moment Eu(4f) to itinerant Co(3d) magnetism

Antiferromagnetism in EuCo2P2 (ThCr2Si2-type structure) is due to ordering of the Eu2+(S-8(7/2)) sublattice moments (T-N = 66.5 K) while the Co(Sd) sublattice does not carry any magnetic moment. EuCo2P2 undergoes a pressure-induced isostructural phase transition at p(c) = 3.1 GPa. Eu-151 high-pressure Mossbauer experiments (0 less than or equal to p less than or equal to 5 GPa) reveal a valence transition of Eu from Eu2+ to nonmagnetic Eu3+(F-7(0)) at p > p(c) with the consequence that the disappearance of the Eu(4f) sublattice magnetism is accompanied by a simultaneous appearance of Co(3d) sublattice magnetism (T-N* = 260 K). The latter is explained by the filling of the 3d states.