Magnetic susceptibility measurements on Li-intercalated graphite: Paramagnetic to diamagnetic transitions in C12Li induced by magnetic field

Although graphite intercalation compounds (GICs) have been received much attention owing to their wide variety of structural, electronic, and physical properties, little is known about changes in magnetism as a function of intercalants. In this paper, we performed magnetic susceptibility (χ) measurements on Li-intercalated compounds, C6Lix, which are currently used as a negative electrode material for lithium-ion batteries. Pristine graphite (x = 0) indicated a large diamagnetic property as reported previously, whereas x = 0.5, 0.61 and 1 samples showed a Pauli paramagnetic property. The magnetic transition from diamagnetic to paramagnetic gradually took place at around x ≥ 0.34, which is inconsistent with the predicted x dependence of the orbital χ based on the tight binding model and the Fukuyama formula. We have found another magnetic transition for x = 0.5 and 0.61, namely that the magnetization at 5 K first increases with increasing field up to ∼3.5 kOe, and then decreases linearly. Because this paramagnetic to diamagnetic transition induced by the field was observed at 300 K, the x = 0.5 and 0.61 samples were found to be applicable for switching devices.

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