Spin blockade, orbital occupation, and charge ordering in La1.5Sr0.5CoO4.
Using Co-L2,3 and O-K x-ray absorption spectroscopy, we reveal that the charge ordering in La1.5Sr0.5CoO4 involves high spin (S=3/2) Co2+ and low spin (S=0) Co3+ ions. This provides evidence for the spin-blockade phenomenon as a source for the extremely insulating nature of the La2-xSrxCoO4 series. The associated e{g}{2} and e{g}{0} orbital occupation accounts for the large contrast in the Co-O bond lengths and, in turn, the high charge ordering temperature. Yet, the low magnetic ordering temperature is naturally explained by the presence of the nonmagnetic (S=0) Co3+ ions. From the identification of the bands we infer that La1.5Sr0.5CoO4 is a narrow band material.
Chang
C F
CF
II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany.
Hu
Z
Z
Wu
Hua
H
Burnus
T
T
Hollmann
N
N
Benomar
M
M
Lorenz
T
T
Tanaka
A
A
Lin
H-J
HJ
Hsieh
H H
HH
Chen
C T
CT
Tjeng
L H
LH