{'fraction_non_alphanumeric': 0.04508856682769726, 'fraction_numerical': 0.03542673107890499, 'mean_word_length': 5.153465346534653, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Metallicity and positive magnetoresistance induced by Pb substitution in a misfit cobaltate crystal

We have synthesized single crystals of the misfit-layered cobalt oxide, [Bi1.5Pb0.5Sr2O4−δ][CoO2]1.86, with quadruple NaCl-type layers, using a flux method, and measured their transport properties. From structural refinements, it is found that the modulation in the BiO layer observed in [Bi1.74Sr2O4−δ]RS[CoO2]1.82 is suppressed by Pb substitution. The in-plane resistivity, thermopower, and Hall coefficient are 4.3 mΩ cm, 101 µV K−1, and 1 × 10−2 cm3 C−1 at 300 K, respectively; these are consistent with those of the misfit-layered cobalt oxides. All of these values are smaller than those of [Bi1.74Sr2O4][CoO2]1.82, indicating that the carrier concentration is larger than that of the undoped crystal. Moreover, the low T upturn of resistivity observed for most of the cobalt misfit oxides is replaced by a metallic behavior, following a T2 dependence, indicating strong correlations in the Pb-doped crystal. Also, the magnetoresistance, usually negative for misfit oxides, is replaced by a small positive magnetoresistance. Doping with Pb is thus an efficient way to suppress the low T localized behavior usually observed for misfits.