A giant Stoner enhancement in the strongly correlated perovskite LaNiO₃

The Stoner enhancement occurs in paramagnetic systems in which electron-electron correlations cause a greater increase of the magnetic susceptibility than the change of the electronic contribution to the specific heat. Moreover, the enhancement is normally a precursor for a transition to a magnetically ordered phase. Under such circumstances, the physical properties are highly sensitive to hydrostatic pressure. We have studied the volume dependence of physical properties for the polycrystalline and single crystal of the oxygen stoichiometric LaNiO₃ prepared under high oxygen pressure. The thermal expansion and the magnetostriction measurements reveal giant electronic Grüneisen parameters γ_e and γ_Χ. These results agree with the measurement of magnetic susceptibility of LaNiO₃ under high pressure. The observed large difference of γ_e between the experimental data and from the DFT calculation at the PBE level further confirms a giant enhancement to the density of state at the Fermi energy due to strong electron correlations in LaNiO₃. In this talk, a comprehensive comparison of physical properties between the polycrystalline and the single crystal samples of LaNiO₃ will also be given.