Experimental and theoretical study of the magnetism and local lattice structure ofdions in alkali-metal hosts

The local susceptibility of isolated Mo ions in Na is observed to be consistent with a localized, magnetic 4d⁵ state of Mo¹⁺. Size, valence, and bonds of such Mo¹⁺ cells are similar to the host Na¹⁺ cells. These features allow a study of 4d magnetism by local-spin-density calculations under the premise of substitutional Mo ions in Na. The calculations yield an effective moment of more than 5μB for Mo in Na. In the larger hosts, K, Rb, and Cs, we propose unusual large lattice contractions around d ions with localized d states, up to 22% for the extreme case of Fe²⁺ in Cs. This results from impurity-host bond strengths larger than those between host atoms along with the very large compressibilities of K, Rb, and Cs.