Antiferromagnetism is a type of magnetic ordering in materials where adjacent atomic spins align in opposite directions. This results in a net magnetic moment of zero, as the opposing spins cancel each other out. Antiferromagnetic materials typically exhibit this behavior at low temperatures and can transition to a paramagnetic state when heated. Common examples of antiferromagnetic materials include iron oxide and manganese oxide. The study of antiferromagnetism is important in fields like solid-state physics and magnetism, as it helps in understanding various magnetic properties and behaviors in different materials.