MAGNETIZATION PROCESS IN THE ANTIFERROMAGNET URU2SI2

The Crystalline-Electric-Field (CEF) based approach with a non-magnetic singlet \-2 > -\+2 >, resulting from higher-order CEF interactions, as the ground state for the H-3(4) multiplet of the U4+ ion provides a very consistent explanation for many experimental features of URu2Si2. The magnetization process in URu2Si2 is discussed in terms of the formation of the U4+-ion moment by external fields taking into consideration the antiferromagnetic interactions. The metamagnetic transition at 36 T originates from crossing of the CEF levels. A scheme for the antiferromagnetic interactions of the U ions, in which the interaction between the 5f spins is mediated by 6d-electron spins, is proposed for U systems.