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Magnetic materials

Which type of magnetism does a material show if its magnetic susceptibility χ is negative and very small, on the order of 10⁻⁵?

  1. ADiamagnetism
  2. BParamagnetism
  3. CAntiferromagnetism
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Answer: A. Diamagnetism

Diamagnetism is the property in which an applied magnetic field changes the orbital motion of electrons and produces a weak magnetization opposite to the field; χ is negative, with a magnitude of about 10⁻⁶ to 10⁻⁵. All materials have it, but in copper, water and most organic substances, which have no unpaired electrons, it is the only magnetism that appears. Paramagnetism is the slight alignment of randomly oriented atomic moments along the field, and χ is positive. Antiferromagnetism is an ordering of neighboring moments antiparallel to one another, and χ is again small and positive. The negative sign of χ is what identifies diamagnetism, and superconductors show perfect diamagnetism with χ = −1.

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