M.Sc. (Semester IV) (CBCS) Examination Mar/Apr-2018
Physics (Materials Science)
MAGNETIC MATERIALS
Time: 2½ Hours
Max. Marks: 70
Instructions: Q.1 and Q.2 are compulsory. Attempt any three questions from Q. 3 to 7. All questions carry equal marks. Use of non-programmable calculator is allowed.
Q.1

Select Correct alternatives:
08
Above the Neel Temperature
The diamagnetism vanishes
The paramagnetism vanishes
The ferrimagnetism vanishes
The antiferromagnetism vanishes
The typical volume of a domain is
10−2
10−6
10−10
10+6
The SrFe12O19 is a
Hexaferrite
Spinel Ferrite
Dielectric
Superconductor
For a ferromagnet
Exchange integral J is positive and spins are parallel
J is negative and spins are parallel
J is negative and spins are antiparallel
J is positive
The magnetization of a solid, magnetic induction and field strength H are related by




Magnetic Susceptibility 1 for a
Metal
Semiconductor
Insulator
Superconductor
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
The typical value of the thickness of the Bloch wall is
1Å
10 Å
100 Å
1000 Å
Page 2 of 2
SLR-UN-495

State True or False
06
Curie law is valid for paramagnet.
The typical volume of a domain is 10−10
Magnetic induction B and magnetic field intensity H are related by
B
The magnetic spin arrangements are explained using Exchange interaction energy.
Exchange interaction between any two electrons is
Fe3O4 is a magnetostrictive material.
Q.2
Write a short note on:
14
ΔE Effect
04
Physical Origin of Crystal Anisotropy
05
Spinel Ferrites
05
Q.3
Explain in detail the quantum theory of paramagnetism.
08
Explain the magnetic properties of garnets with suitable example.
06
Q.4
Discuss the magnetic characteristics of diamagnetic, paramagnetic, ferromagnetic, 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
Give an account for molecular filed theory of ferromagnetism.
08
Magnetic measurements in closed circuits.
06
Q.6
Define magnetostriction and discuss the physical origin of magnetostriction
08
Exchange forces
06
Q.7
Explain the molecular field theory above and below TN in antiferromagnetism.
08
Write a short note on domain wall motion.
06