Tuning Ferro- and Metamagnetic Transitions in Rare-Earth Cobalt Phosphides La1−x Pr x Co2P2

A family of rare-earth cobalt phosphides La1− x Pr x Co2P2 (0 ≤ x ≤ 1) that belong to the ThCr2Si2 structure type has been prepared and characterized by structural and magnetic methods and electronic band structure calculations. All studied quaternary phases exhibit multiple magnetic transitions, leading to an observation of ferro- and metamagnetism and magnetic pole reversal. The ferromagnetic transition temperature of LaCo2P2 (132 K) increases dramatically upon substitution of Pr for La and reaches 268 K for La0.25Pr0.75Co2P2. This increase is accompanied by elongation of intralayer Co−Co distances. Variable temperature X-ray diffraction data revealed that temperature dependences of unit cell parameters, and, correspondingly, both intra- and interlayer Co−Co separations show anomalous changes at temperatures close to the ferromagnetic transition. The electronic structure calculations reveal a strong peak in the nonmagnetic density of states (DOS). This instability is removed in the spin-polarized DOS due to the splitting of the majority and minority spin subbands, in accord with the ferromagnetic ordering in the [Co2P2] layer.