Anti-Ferromagnetism

ANTI-FERROMAGNETISM

Antiferromagnetism is a new type of magnetism in which the spins are aligned in antiparallel manner (Fig. 3.28) due to unfavourable exchange interaction among them, resulting in zero magnetic moment. Even when the field is increased, it has almost zero induced magnetic moment.

Properties

1. The susceptibility is very small and is positive. It is given by

X = C / T+Ɵ for T > T_N where T_N is the Neel temperature.

2. Initially, the susceptibility increases slightly as the temperature increases and beyond a particular temperature, known as Neel temperature, the susceptibility decreases with temperature.

Antiferro-magnetic materials

(i) Ferrous oxide (FeO)

(ii) Manganese Oxide (MnO₄)

(iii) Manganese Sulphide (MnS)

(iv) Chromium Oxide (Cr₂O₃)

(v) Ferrous Chloride (FeCl₂) and salts of transition elements.

These elements will be wide range of applications in magnetic storage devices.