title: Electronic transitions in perovskite: possible nonconvecting layers in the lower mantle.
abstract: We measured the spin state of iron in magnesium silicate perovskite (Mg(0.9),Fe(0.1))SiO(3) at high pressure and found two electronic transitions occurring at 70 gigapascals and at 120 gigapascals, corresponding to partial and full electron pairing in iron, respectively. The proportion of iron in the low spin state thus grows with depth, increasing the transparency of the mantle in the infrared region, with a maximum at pressures consistent with the D" layer above the core-mantle boundary. The resulting increase in radiative thermal conductivity suggests the existence of nonconvecting layers in the lowermost mantle.
authors.affiliation: Laboratoire de Minéralogie Cristallographie de Paris (UMR CNRS 7590), Institut de Physique du Globe de Paris, Université Paris, 6 and 7, 4 Place Jussieu, 75252 Paris, France. james.badro@lmcp.jussieu.fr
authors.forename: James
authors.initials: J
authors.lastname: Badro
authors.forename: Jean-Pascal
authors.initials: JP
authors.lastname: Rueff
authors.forename: György
authors.initials: G
authors.lastname: Vankó
authors.forename: Giulio
authors.initials: G
authors.lastname: Monaco
authors.forename: Guillaume
authors.initials: G
authors.lastname: Fiquet
authors.forename: François
authors.initials: F
authors.lastname: Guyot