What is Ferromagnetism ? Behaviour of Ferromagnetic Substances & the Elements which exhibit Ferromagnetism..!

FERROMAGNETISM

a) The term Ferromagnetism was coined by Curie Pierre in 1895 .

b) Those substances which when placed in a magnetic field, are strongly magnetised in the direction of the applied field are called as Ferromagnetic substances.

c) A Ferromagnetic substance when placed in a non-uniform magnetic field, show a very strong tendency to move from the weaker to the stronger parts of the magnetic field.

d) Ferromagnetic materials are made up of atoms with permanent dipole moments.

e) Ferromagnetic substances retain their magnetism even when the external magnetic field is removed. This tendency of Ferromagnetic substances to remember their magnetic history is called as " Hysteresis " .

f) Due to their this property Ferromagnetic substances can be converted into Permanant Magnets.

g) Being Permanant magnets the Ferromagnetic substances can give rise to a magnetic field even in the absence of an external magnetic field.

h) Ferromagnetic substances have very high Magnetic Susceptibilities, ranging from 1000 to 1,00,000 .

i) The Relative Permeability of the Ferromagnetic substances is much more greater than 1 and hence for a Ferromagnetic substance the magnetic lines of force are strongly attracted.

j) When a Ferromagnetic substance is heated above a certain temperature it loses it's ferromagnetism and become Paramagnetic.

k) The temperature at which a Ferromagnetic substance becomes Paramagnetic is called as Curie Temperature.

l) Ferromagnetism is exhibited by solid materials only.

Elements from the Periodic Table which exhibit Ferromagnetism are :-

1) Iron

2) Cobalt

3) Nickel

4) Gadolinium

Anti-Ferromagnetism

a) Antiferromagnetism was first discovered by Neel and Bitter and later extended by Van Vleck.

b) In the presence of a strong magnetic field, Antiferromagnetic materials are weakly magnetised in the direction of the applied field.

c) In Antiferromagnetic materials, the magnetic moments are aligned in opposite directions and are equal in magnitude.

d) Due to this the magnetic moments of the neighbouring atoms cancel each other and its net magnetisation is zero.

e) Antiferromagnetism occur commonly among transition metal compounds, especially oxides.

f) Antiferromagnetism generaly exist at low temperatures and vanishes at and above a certain temperature called the Neel temperature .

g) Above the Neel temperature, the Antiferromagnetic material is typically paramagnetic .

h) Chromium is an example of element which exhibit Antiferromagnetism.

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What is Paramagnetism ? Behaviour of Paramagnetic Substances & the Elements which exhibit Paramagnetism..!

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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What is Diamagnetism ? Behaviour of Diamagnetic Substances & the Elements which exhibit Diamagnetism..!

Diamagnetism

a) The term Diamagnetism was coined by Michael Faraday in 1845 .

b) Those substances which when placed in a magnetic field, are weekly magnetised in a direction opposite to that of the magnetising field are called as Diamagnetic Substances .

c) When a Diamagnetic substance is placed in a non-uniform magnetic field , it's atoms acquire a small magnetic dipole moment in a direction opposite to that of the magnetic field .

d) As a result , the Diamagnetic substances moves from stronger part of the magnetic field to it's weaker part i.e. they are weakly repelled by the magnet .

e) The Diamagnetic substances do not retain their magnetic properties when the external magnetic field is removed.

f) Diamagnetism is usually observed in Solids composed of atoms with completely filled electronic shells .

g) The reason is that in a completely filled shell there are equal number of electrons with positive and negative spins, so that the total magnetic moment is zero .

h) This is the reason why the individual atoms in a Diamagnetic substance do not posses any net magnetic dipole moment.

i) The magnetic susceptibility of a Diamagnetic substance has a small negative value.

j) The relative permeability of a Diamagnetic substance is slightly less than 1.

k) The behaviour of a Diamagnetic substance is independent of temperature.

l) That is why Magnetic susceptibility of Diamagnetic substances do not change with temperature and hence the Diamagnetic substances do not obey Curie's Law .

m) The Diamagnetic substances when placed in a uniform magnetic field, they set their longest axis at right angles to the direction of the field and the shortest axis along the direction of the field.

n) Orbital motion of electrons is the root cause of magnetism in Diamagnetic substances.

o) All Substances are Diamagnetic to some extent .

Elements from the Periodic Table which exhibit Diamagnetism are :-

1) Hydrogen

2) Helium

3) Beryllium

4) Boron

5) Carbon

6) Nitrogen

7) Neon

8) Silicon

9) Phosphorus

10) Sulphur

11) Chlorine

12) Argon

13) Copper

14) Zinc

15) Gallium

16) Germanium

17) Arsenic

18) Selenium

19) Bromine

20) Krypton

21) Silver

22) Cadmium

23) Indium

24) Antimony

25) Tellurium

26) Xenon

27) Gold

28) Mercury

29) Thallium

30) Lead

31) Bismuth

Of this all elements Bismuth and carbon graphite are the strongest Diamagnetic materials.

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