Pressure-induced spin state crossover in layered cobaltite LaSrCoO<inf>4</inf>

Abstract

© 2019 Elsevier B.V. The crystal structure of the tetragonal layered cobalt oxide LaSrCoO4 has been studied by means of neutron diffraction at high pressures up to 5.8 GPa in temperature range 7–300 K. The pressure and temperature behaviour of the lattice parameters, including lattice parameters, unit cell volume, and interatomic bond lengths, have been obtained. The anisotropic compression of lattice parameters as well as Co-O bond lengths of the oxygen octahedra have been revealed. The anomalous thermal volume expansion at high pressure are observed, indicative for the pressure induced spin state crossover of Co3+ ions from the mixed low spin – high spin (LS + HS) state at room temperature towards the low spin (LS) ground state. The structural mechanisms of the spin state crossover are discussed.