RARE-EARTH MAGNETIC-ORDERING IN THE R2CUO4 CUPRATES (R = TB, DY, HO, ER AND TM)

Low-temperature AC magnetic susceptibility measurements on the heavy r are-earth antiferromapetic cuprates R2CuO4 which have a T' Nd2CuO4-lik e crystal structure are reported. A single susceptibility maximum is o bserved in all the compounds at different temperatures ranging from 1. 5 K to 10 K, which is interpreted as indicative of antiferromagnetic l ong-range ordering of the rare-earth ions. No double peak structure is observed in any of these weak ferromagnetic compounds, at variance wi th the weak ferromagnetic compound Gd2CuO4 for which a second sudden t ransition, of uncertain origin, has been previously observed at T(L) a lmost-equal-to 20 K. The overall dependance of the antiferromagnetic o rdering temperature on the single ion rare-earth magnetic moments do n ot follow a simple scaling with the De Gennes factor but rather a scal ing with the full rare-earth magnetic moments, suggesting a pseudo-dip olar origin for the leading magnetic interaction coupling the rare-ear th ions. Some important deviations are observed, however, which may be indicative of strong crystal field effects. It is suggested that the Suhl-Nakamura mechanism may ba a relevant mechanism to understand the rare-earth magnetic ordering in the R2CuO4 series (R = Nd- Tm).