= Solution
A macroscopic nickel specimen can split into <magnetic domains>, each with nonzero local <spontaneous magnetization> but with different orientations. Their vector contributions can cancel, giving an almost zero measured net <magnetization> below the <Curie temperature>. This reduces the external stray-field energy, at the expense of <magnetic domain wall> energy; the balance favours a multidomain state in many ordinary specimens.
An applied <magnetic field> can move <magnetic domain walls> and rotate the domain moments, revealing a large response and eventually <saturation magnetization>. Thus a zero average does not mean that each local moment has become thermally disordered or that the material is above its <Curie temperature>. Preparation, shape and domain-wall pinning influence remanence.
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