The role of a critical distance in RMn/sub 2/ compounds

In the RMn/sub 2/ system, the antiferromagnetically ordered Mn moments are reported to disappear at a reduction of the Mn-Mn distance, either by applying external pressure or by alloying. We illustrate the phenomena for the hexagonal NdMn/sub 2/ compound. The Neel temperature in the (Nd,Lu)Mn/sub 2/ system is found to vanish; at substitution of 30% of Nd by Lu, considered to be equivalent-to applying a pressure of 24.5 kbar. Antiferromagnetic order of the Mn sublattice, however, vanishes already at substitution of 7% of Mn by Cu and of 3% of Mn by Fe in the NdMn/sub 2/, being equivalent to an external pressure of only 4 kbar. High-pressure studies on the Nd(Mn,Cu)2 system show that the effect of an external pressure on the Neel temperature decreases markedly with increasing Cu concentration, in contrast to what is expected in a critical distance model.<
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