Experimental Evidence for Interband Mixing in Rare‐Earth Intermetallic Compounds

Measurements of the Knight shifts and susceptibilities of rare‐earth intermetallic compounds have been extended to YCu, GdCu, TbCu, DyCu, HoCu, and ErCu. The phenomenological exchange constants 𝒥sf between 4f‐electron spins and conduction‐electron spins are derived to be −0.21 eV. Also the paramagnetic Curie temperatures of the compounds GdCu1−xGax have been measured. The Knight shifts and Curie temperatures are discussed in terms of the Ruderman‐Kittel‐Kasuya‐Yosida theory. For the various series of rare‐earth intermetallic compounds the s‐f exchange integral Γ = 2 J(0) and the Fermi wave vector kF have been determined. Γ is found to be a continuous function of kF, with a sign reversal at kF ≈ 1.4 Å−1. This observed behavior is consistent with the calculations of Watson, Koide, Peter, and Freeman on the effect of interband mixing on the exchange interactions.