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NiO is antiferromagnetic. But on heating...

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

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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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