Hyperfine Enhanced Nuclear Antiferromagnetism in PrS, PrTe, and PrBi

We have investigated the strongly correlated electronic and nuclear magnetic properties of the cubic Van Vleck paramagnets PrS, PrTe, and PrBi by means of SQUID magnetometry at 2 K≤T≤300 K as well as ac susceptometry at ultralow temperatures, 0.06 mK≤T ≤100 mK. We observe magnetic ordering transitions of the hyperfine enhanced magnetic moments of the ¹⁴¹Pr nuclei in all three compounds. Our ac susceptibility data taken at ultralow temperatures point to antiferromagnetic ground states. The observed Neel temperatures, T_N(PrS, PrTe, PrBi) = 0.09, 0.60, 1.20 mK, scale with the size of the Van Vleck susceptiblity and related hyperfine enhancement factor respectively. The nuclear fcc spin-5\2 antiferromagnets PrS, PrTe, and PrBi are promising candidates for interesting spin structures. Currently we use the metallurgical possibility to substitute Pr by La and Pb in these compounds in order to study the multiple interplay between electronic magnetism, nuclear magnetism, superconductivity (e.g. in Pr_1-xLa_xTe), and semiconductivity (e.g. in Pr_1-xPb_xTe).