Competing interactions in ErxPr(1-x)Co2

Abstract

Among the rare-earth (R) - transition metal (T) intermetallics, the Co Laves phases are particularly interesting because of the magnetism of the 3d band in these systems is strongly influenced by the R sublattice magnetization. If the R bears a magnetic moment, the f-d exchange results in a ferro- (light R) or ferrimagnetic (heavy R) coupling between the Co and the R magnetization sublattices. High magnetic fields force ferrimagnetic RCo2 to gradually change the antiparallel alignment between the R and the Co moments towards a ferromagnetic phase. In particular, for ErCo2a transition at 52 T has been reported, which was identified as Itinerant Electron Metamagnetism (IIEM). On the other hand, in ferromagnetic systems (as PrCo2) no field induced transition has been detected. The local interactions can be modified by substituting Er by Pr, changing the internal exchange fields to give rise to spin flipping transitions. In this work we have systematically measured the low-temperature high-field magnetization of ErxPr(1-x)Co2 at 4, 10, and 40 K at the Dresden High Magnetic Field Laboratory. Er substitution by Pr sets the condition for the system to undergo a field induced phase transition, ranging between 22 T (x=0.1) and 50 T (x=0.9). A clear jump in magnetization is observed in every diluted system. The modification on the internal exchange fields with increasing x plays the major role in modifying the critical field. The magnetization of the ErxPr(1-x)Co2 series at low field is very well described by an antiferromagnetic disposition of the Er and Pr ions (μEr ≈ 7μB > μPr ≈ 3μB). At high field may be described by an ferromagnetic disposition of the Er and Pr ions and a small Co component (μEr ≈ 7μB >μPr ≈3μB >μCo ≈0.5μB).