Inversion and suppression of an oxygen bulk phase transition in confined geometry

Abstract.By means of susceptibility experiments on oxygen confined to the pores of a Gelsil substrate we investigated the bulk γ-β transition. At low fillings, the transformation is completely suppressed. At higher but still incomplete filling we observe a partial transformation from γ to β on cooling and a subsequent inverted transition on heating, i.e. the transformation of γ-phase material into the β-phase upon heating. At 100% filling this inversion disappears. We discuss our results on the basis of geometric considerations.