Question

How many of the following compounds show ferrimagnetism?
$Fe _{3} O _{4} ; MgFe _{2} O _{4} ; NiFe _{2} O _{4} ; MnO ; CrO _{2}$

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

Answer: (C)

In ferrimagnetic substances, the magnetic moments of the domains are alligned in parallel and antiparallel directions in unequal number. The net magnetic moment is small. Thus, these are weakly attracted by magnetic field than ferromagnetic substances and these also lose ferrimagnetism on heating and become paramagnetic. e.g. $Fe _{3} O _{4}$ and ferrites like $ZnFe _{2} O _{4}, MgFe _{2} O _{4}$ and $NiFe _{2} O _{4}$ etc.



Among the given options, we have $3$ compounds ( i.e. $Fe _{3} O _{4}, MgFe _{2} O _{4}$ and $\left.NiFe _{2} O _{4}\right)$ that show ferrimagnetism.