【学术视频】第八届国际磁科学会议 | 日本京都大学Tsunehisa Kimura教授

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The electric current J of the system (a) induced by the applied ac magnetic field 𝐁̇(𝑡) is described by an RL electric circuit composed of the self-inductance L due to a coil formed by the orbital motion of electron and the resistance R due to thermal noise. Then, the response J and the resultant magnetization M is derived. We obtained the diamagnetic susceptibility 𝛾 for Faraday diamagnetism as follows: 𝛾 = 2𝐾𝜒 

where 𝜒 is the Langevin susceptibility and 𝐾 is Nagaoka constant ( 0 ≤ 𝐾 ≤ 1 ). The total susceptibility measured experimentally is 𝜒 + 𝛾, indicating that diamagnetism is enhanced.

Due to this enhancement, the anisotropic susceptibility ∆𝜒 + ∆𝛾 might also increase under ac magnetic field. We performed magnetic orientation of microcrystals of L-alanine under rotating magnetic fields and obtained a result, ∆𝛾/ ∆𝜒=0.94. This is consistent with the theoretical prediction above.