NiO is antiferromagnetic. But on heating...

`NiO` is antiferromagnetic. But on heating at `250°C`, it becomes paramagnetic. Why?

Text Solution

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In solid state, the magnetic moments of `NiO` are aligned in such a fashion, such that the net moment is zero. So, NiO is antiferromagnetic.
On heating, the alignment is disturbed. The domains are randomized. `Ni^(2+)` has `d^(8)` configuration with unpaired electrons, hence, exhibits paramagnetism.

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The temperature at which a ferromagnetic material becomes paramagnetic is called

Neutral temperature

Curie temperature

Inversion temperature

None of these