What is antiferromagnetic material?

Hint: Magnetic materials are those which show magnetic properties like they attract other metals. The magnetic property of the element depends upon the orientation of the electrons in the valence shell. Some elements show permanent magnetism while some show temporary magnetism.

Complete answer:
The materials which show anti ferromagnetism are called antiferromagnetic materials. When these substances are placed in an external magnetic field the electrons of metal ions arrange themselves in a opposite direction to that of the magnetic field throughout the material thus as a result it exhibits no external magnetism. Here the magnetism is cancelled out by the inner magnetic particles as they are aligned reversely. This antiparallel nature of antiferromagnetic material has disappeared above a temperature called Neel temperature. According to the Neel temperature above, the antiferromagnetic substance shows some extent of magnetism. Above this temperature the thermal excitation prevents the electron from arranging in an antiparallel direction and thus shows some magnetism above this temperature.
Thus when these materials are kept in the external magnetic field they get magnetized in the direction of the applied magnetic field. The most common examples of such compounds can be found among the transition metals. Hematite, chromium , alloys of iron and manganese also show the property of anti -ferromagnetism. Thus when anti ferromagnetic materials are demagnetized then they lose their magnetic property completely.

Note:
The Neel temperature may vary according to the metal. Above this temperature they start showing some magnetic properties which are temporary .Thus when temperature decreases below it then it does not show magnetic properties.