Suppression of the enhanced paramagnetic thermal expansion of YMn2 by Fe substitutions

The thermal expansion coefficient alpha of YMn2 just above its Neel temperature (T-N = 90 K) is about 45 x 10(-6) K-1, it takes a value of 53 x 10(-6) K-1 at room temperature and passes through a maximum around 350 K. This unusual behaviour of alpha(T) and the higher value (if compared with other known spin fluctuation systems such as YCo2) has been attributed to electronic instabilities of the Mn ions. In the present investigation it is shown that - when changing the environment of an individual Mn ion by substituting Mn by Fe-alpha decreases very quickly with increasing Fe content. This has been considered as a proof that the electronic instabilities of the Mn ions depend very sensitively on the surroundings. (C) 1998 Elsevier Science B.V. All rights reserved.