PARAMAGNETISM
a) The term Paramagnetism was coined by Curie Pierre in 1895.
b) Those substances which when placed in a magnetic field are weakly magnetized in the direction of the applied field are called as Paramagnetic Substances .
c) A Paramagnetic Substance when placed in a non-uniform magnetic field, begins to move form the weaker region to the stronger region of the magnetic field.
d) Thus the magnetic field lines prefer to pass through the Paramagnetic substances and this is the reason why the Paramagnetic Substances are weekly attracted by a magnet.
e) When a rod of Paramagnetic substance is suspended freely in a uniform magnetic field, the rod comes to rest with its axis parallel to the applied field.
f) Paramagnetism is generally exhibited by the elements due to the presence of unpaired electrons.
g) The reason is that an unpaired electron being lonely can spin in any direction ,i.e., it can assign its magnetic moment in either positive or negative direction. Due to this there will be unequal number of positive and negative spins and hence after the cancellation of the opposite spins there will be some residual magnetic moment . This is the reason why in a Paramagnetic substance, the individual atoms / molecules / ions have small net magnetic moment.
h) The Magnetic Susceptibility of a Paramagnetic substance have a small positive value.
i) The Relative Permeability of Paramagnetic substances is slightly greater than 1 .
j) Paramagnetic substances lose their magnetism as soon as the external magnetic field is removed.Thus the total magnetization drops to zero when the applied field is removed.
k) The Magnetization of the Paramagnetic substances decreases with the increase in temperature.
l) Paramagnetism is normally stronger than Diamagnetism .
m) Below the Curie temperature , certain Paramagnetic materials exhibit Ferromagnetism .
n) All the three states of matter exhibit Paramagnetism. eg :- Aluminium,Oxygen,Platinum.
Elements from the Periodic Table which exhibit Paramagnetism are :-
1)
Lithium
2)
Oxygen
3)
Sodium
4)
Magnesium
5)
Aluminium
6)
Calcium
7)
Titanium
8)
Manganese
9)
Strontium
10)
Zirconium
11)
Molybdenum
12)
Ruthenium
13)
Rhodium
14)
Palladium
15)
Tin
16)
Barium
17)
Cerium
18)
Neodymium
19)
Samarium
20)
Europium
21)
Terbium
22)
Dysprosium
23)
Holmium
24)
Erbium
25)
Thulium
26)
Tungsten
27)
Osmium
28)
Iridium
29)
Platinum
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