question_answer 50)

Explain the following with suitable examples : (i) Ferromagnetism                        (ii) Paramagnetism (iii) Ferrimagnetism                       (iv) Antiferromagnetism  

Answer:

(i) Ferromagnetism. A substance which is strongly attracted by the magnetic field and shows magnetism even in the absence of magnetic field is called Ferromagnetic substance. e.g., Fe, Ni, Co etc. Ferromagnetism arises due to the spontaneous alignment of magnetic moments due to unpaired electrons in the same direction. CrO2 is ferromagnetic oxide used to make magnetic tapes for cassette recorders. (ii) Paramagnetism. A substance which is weakly attracted by the magnetic field is called paramagnetic substance and the property thus exhibited is called paramagnetism. This property is due to the presence of unpaired electrons. e.g., Cu2+, O2. These substances lose their magnetism in the absence of the magnetic field. (iii) Ferrimagnetism. If the magnetic moments arc aligned in parallel and antiparallel directions in unequal number resulting in a small net magnetic moment, the substance is called ferrimagnetic substance and the property thus exhibited is known as ferrimagnetism e.g., .                       Ferromagnetic      Antifcrromagnetic               Ferrimagnetic (iv) Antiferromagnetism. Certain paramagnetic substances allign the magnetic moments due to the unpaired electrons under the influence of 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-ferromgnetism. Managanese oxide (MnO) is anti-ferromagnetic in nature. (v) 12-16 and 13-15 Compounds The solid binary compounds prepared by combining elements of group 12 and 16 are called 12-16 compound e.g. ZnS and CdS those prepared by combining elements O, group 13 and 15 are called 13-15 compounds e.g. AIP and GaAs. These are used as semiconductors.