Question

Which substance shows antiferromagnetic?
A.\[Zr{O_2}\]
B.$CdO$
C.\[Cr{O_2}\]
D.\[M{n_2}{O_2}\]

Answer 1

Hint: Certain paramagnetic substances that align the magnetic moments because of the unpaired electrons under the influence of an external magnetic field in such a way that they mutually cancel. As a result, they possess zero or no magnetic moment. Such substances are known as anti-ferromagnetic substances and this property is called anti-ferromagnetism.

Complete answer:
Antiferromagnetic is a type of magnetism in solids in which adjacent ions behave as a tiny magnet. These ions align themselves at low temperature.
For Example - Manganese oxide (MnO) is anti-ferromagnetic in nature in which adjacent ions that behave as tiny magnets (in this case manganese ions, \[M{n^{2 + }}\]) spontaneously align themselves at relatively low temperatures into opposite, or antiparallel, arrangements throughout the material so that it exhibits.
Antiferromagnetic materials occur commonly among transition metal compounds, especially oxides. Examples include hematite, metals such as chromium, alloys such as iron manganese (FeMn), and oxides such as nickel oxide (NiO). Antiferromagnetic solids exhibit special behaviour in an applied magnetic field which depends upon the temperature, such as at very low temperatures, the solid exhibits no response to the external field, because the antiparallel ordering of atomic magnets is rigidly maintained and at higher temperatures, some atoms break free of the orderly arrangement and align with the external field.
MnO, $M{n_2}{O_3}$ ​ shows anti-ferromagnetism. Equal number of unpaired electrons are aligned in opposite directions, their magnetic moment (electron spin) will compensate for each other's magnetic moment.
Ni, Fe, Co and \[Cr{O_2}\] shows ferromagnetism.

Therefore, the correct answer is option (D).

Note: A ferromagnetic substance is strongly attracted by the magnetic field and shows magnetism even in the absence of magnetic field. e.g., Fe, Ni, Co etc. Ferromagnetism arises due to the spontaneous alignment of magnetic moments due to unpaired electrons in the same direction.