Search for pressure-induced tricriticality in Cr

We investigate the possibility of reducing the phase space of magnetic fluctuations at the weakly first-order Néel transition in Cr by neutron diffraction to test whether a second-order phase transition can be induced under the application of uniaxial pressure. Using an improved setup to reduce stress inhomogeneities we succeed in increasing significantly the pressure range until irreversible broadening due to plastic deformation occurs compared with previous studies. Despite the observed tripling of the intensity of the magnetic Bragg peak (0,0,1-δ) at p[110]≥450 bar, indicating a full population of a single-Q±-domain state, no hints of a tricritical point are observed, i.e., the phase transition remains weakly first order. Therefore, the reduction in the phase space of the magnetic fluctuations by uniaxial pressure does not lead to the predicted second-order phase transition.