Resonant photoemission of single-crystal RBaCo2O5+δ (R=Gd, Dy)

Large single crystals of LnBaCo2O5.5: Initial nucleation, growth and study

“…A number of mechanisms have been proposed for the MI transition [8,[14][15][16][17], and not all of these can be distinguished through photoemission. However, the very gradual changes observed in the spectra as a function of temperature, particularly in the region of 2 eV binding energy (a region associated with the Co(III) low spin (LS, S=0) state [13]), suggest that the transition does not occur via a sudden change from LS to the high spin (HS, S ¼ 2) spin switch as proposed by Frontera et al [14]. This conclusion agrees well with the recent assertion (based on the measured X-ray absorption spectra) on the absence of the spin-state transition in the vicinity of the MI transition in Tb-112 single crystals [8].…”

“…5. Peak D in this figure has been shown to arise mainly from Gd 4f states, whereas peaks A-C contain contributions from Co 3d states [13]. Constant initial states (CIS) spectra in the region of the O 2s threshold (in the region of 22-24 eV photon energy) were generated from the VB EDCs.…”

Switching from unusual to usual ferromagnetism in “112” LnBaCo2O5.50±δ: By calcium doping

“…In between these ladders, the sixsided tunnels are occupied by Ln 3+ cations [3,12]. Such a structure is very flexible and sensitive to tiny variations of the oxygen content as well as to the size of the Ln 3+ cation, leading to dramatic variations of the magnetic properties [10,12,17,[19][20][21]. For the oxygen content ''O 5.50 '' all cobalts are in +3 valence state.…”

Effect of oxygen content on magnetic properties of layered cobaltites PrBaCo2O5+δ

“…On the basis of neutron diffraction [13,[18][19][20] with different types of antiferromagnetic SSO [15]. Density functional calculations [11,22] and resonant photoemission studies [23] suggest that there is a strong hybridization between O-2p and Co-3d orbitals with a narrow charge transfer gap near Fermi level. With increasing temperature, the pdσ hybridized hole in the O-2p valence band suffers a gradual delocalization leading to successive magnetic transitions and spin reorientations.…”