^59Co-NMR Studies on La_4Co_3O_10+δ(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

概要

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Samples of La_4Co_3O_10+δ with δ〜0.1,0.3 and 0.6 have been prepared. For δ〜0.1,the crossover-like changes of the spin state at〜100K and 〜550K have been confirmed by the measurements of the magnetic susceptibility. At〜550K, we have observed for the sample the anomalous T-dependence of the electrical resistivity and the thermoelectric power. Its NMR spectra exhibit the very large broadening at low temperatures due to the antiferromagnetic ordering. NMR spectra of the sample with δ〜0.6 show that there exist two kinds of Co atoms:The NMR signal intensity of one of the two with the larger relaxation rate 1/T_2 decreases, while the intensity of the other with the smaller 1/T_2 increases,with decreasing T below 100K, which indicates that the spectra of the latter are from the Co^3+ in the low spin state. The T-dependence of 1/T_1 shows the existence of the energy difference between the low spin (spin S = 0) and intermediate spin (S = 1) states of the order of 100K.
社団法人日本物理学会の論文
2002-12-15