Q.Which of the following is a ferromagnetic substance ?

Iron (Fe) is ferromagnetic; Cu is (weakly) diamagnetic, NaCl is diamagnetic, and MnO is antiferromagnetic.

Ferromagnetic substances have their magnetic domains aligned in the same direction and show strong permanent magnetism. Classic examples are Fe, Co, Ni and their alloys.

• Fe: ferromagnetic …

Fe3O4 (magnetite) is ferromagnetic; NaCl is diamagnetic, and O2 and N2 are gases (O2 paramagnetic, N2 diamagnetic) — none show ferromagnetism.

Ferromagnetic substances have permanently aligned magnetic domains and are strongly attracted by a magnetic field (e.g. Fe, Co, Ni, CrO2, and iron oxides).

• NaCl: an ionic solid with all electrons paired → diamagnetic. …