M.Sc. (Semester IV) (CBCS) Examination Oct/Nov-2017
Material Science
MAGNETIC MATERIALS
Day Date: Wednesday, 22-11-2017 Max. Marks: 70
Time: 02.30 PM to 05.00 PM
Instructions: and are compulsory.
Answer any three questions from Q.3 to Q.7.
All questions carry equal marks.
Use of non-programmable calculator is allowed.
Q.1 Objective questions: 08
In nickel-zinc ferrite with Zn/Ni atom ratio equal to the number of
unpaired electron spins present per



2− is (assume
that zinc ions push the ferric ions from tetrahedral sites to octahedral
sites and changes their spins)
5 3.75
1.25 4.5
Exchange interaction between any two electrons is


The phenomenon in which a change in the shape of certain
ferromagnetic material is produced when they are subjected a
magnetic field, in known as
Electrostriction Magnetostriction
Piezoelectric effect Anisotropic effect
Curie law is valid for
Diamagnet Paramagnet
Ferromagnet All substances
At Neel temperature
Susceptibility is maximum
Susceptibility is minimum but not zero
Susceptibility is zero
None of these
The typical value of the thickness of the Bloch Wall is
1 Å 10 Å
100 Å 1000 Å
If is the Neet temperature for an antiferromagnet, its susceptibility
is given by












Page 2 of 2
SLR-MO-541
The orbital angular magnetization of an electron in .
State True or False/ Fill in the blanks: 06
Fe3O4 is a magnetostrictive material.
Magnetic induction B and magnetic field intensity H are related by

For a ferromagnet, Exchange integral J is positive and spins are
parallel.
The typical value of the thickness of the Bloch wall is 1000Å.
Magnetic susceptibility for a metal.
The typical volume of domain its 10-10 m3.
Q.2 Write short notes: 14
Application of magnetostriction. 04
Gouys method to determine the magnetic susceptibility. 05
Polycrystalline materials. 05
Q.3 Give an account for molecular field theory of ferromagnetism. 08
Explain the magnetic properties of garnets with suitable example. 06
Q.4 Discuss the magnetic characteristics of diamagnetic, paramagnetic,
ferromagnetic, and antiferromagnetic and ferrimagnetic materials on
account of their magnetic moments as well as magnetic susceptibilities.
08
Write a short note on antiferromagnetic alloys. 06
Q.5 Discuss the spinel cubic structure of ferrites and explain how the
saturation magnetization of ferrites depends on the site occupancy of A
and B site of spinel lattice.
08
Discuss any method used for the determination of magnetic
susceptibility.
06
Q.6 Define magnetostriction and discuss the physical origin of
magnetostriction.
08
Write short note on Exchange forces. 06
Q.7 Explain the molecular field theory above and below TN in
antiferromagetism.
08
Write a short note Δ E Effect. 06