Spin blockade, orbital occupation and charge ordering in La_(1.5)Sr_(0.5)CoO4

Abstract

Using Co-L_(2,3) and O-K x-ray absorption spectroscopy, we reveal that the charge ordering in La_(1.5)Sr_(0.5)CoO4 involves high spin (S=3/2) Co^2+ and low spin (S=0) Co^3+ ions. This provides evidence for the spin blockade phenomenon as a source for the extremely insulating nature of the La_(2-x)Sr_(x)CoO4 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 non-magnetic (S=0) Co^3+ ions. From the identification of the bands we infer that La_(1.5)Sr_(0.5)CoO4 is a narrow band material.

5 pages, 3 figures

References in corpus (5)

• The spin state transition in LaCoO${}_3$; revising a revision
• A different look at the spin state of Co${}^{3+}$ ions in CoO${}_5$ pyramidal coordination
• Valence, spin, and orbital state of the Co ions in the one-dimensional Ca3Co2O6: an x-ray absorption and magnetic circular dichroism study
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Cited by in corpus (2)

• Electronic and magnetic properties of the kagome systems YBaCo4O7 and YBaCo3MO7 (M=Al, Fe)
• Magnetic order and dynamics of the charge-ordered antiferromagnet La1.5Sr0.5CoO4