Influence of uniaxial tension on antiferromagnetic transformation in europium

An anomalous electrical resistance of Eu near the Neel point was studied under a tensile stress (σ = = 0.25-0.5 kbar) sufficient to decrease the number of components of the order parameter from 12 to 4. It is found that in the «fourcomponent» state the antiferrumagnetic transition remains the first order transition in accordance with theoretical concepts. Along with the first-order transition domain, there is a wide temperature region where the derivative of resistance is described by a power function of the reduced temperature. In this region the stable value of the critical index λ = 0.5±0.05 found for a nondeformed sample can be explained by the influence of the Gaussian tricritical point. After the sample transition into the «fourcomponent» state, the critical index decreases down to λ = 0.2-0.3.