Magnetism

What is magnetism?

Magnetism is one of the phenomena by which materials exert an attractive or repulsive force on other materials.

What causes magnetism in material?

It is the unpaired electrons in the electron orbit cause magnetism

Examples of paired and unpaired electron

N is unpaired

O is paired (one of them)

How do you know which electron orbital is paired or un-paired?

Electrons fall into electron shell according to Hund¡¦s rule. Remember SPDF?? (Chem 11)

Example

1S1 2S2 2P3

		Right
	Wrong
	Wrong

There are four types of magnetism

1.Ferromagnetic

2.Paramagnetic

3.Diamagnetic

4.Ferrimagnetic (Not going to cover)

-Ferrimagnetic is too hard to understand at a high school level

Measurements of magnetism

Magnetism is Measure in Magnetic Susceptibility

The more susceptibility of a material has, the more magnetic property it processes

Magnetic Susceptibility is to measure the magnetic property of a material

Q: What is the differences between some of the materials in the chart above

A: They split off into three groups:

#1 negative value with small Magnetic Susceptibility

#2 positive value with small Magnetic Susceptibility

#3 positive value with relatively big Magnetic Susceptibility compare to above #1 and #2

#4 Zero Magnetic Susceptibility for Vacuum because vacuum does not contain any material

Ferromagnetic

Any material that possess magnetization WITHOUT an external magnetic field (current running through a solenoid) is ferromagnetic. They have large and positive susceptibility. Iron and Cobalt are both examples of ferromagnetic materials. They do not need an external field because these materials produce their own magnetic field. Some ferromagnetic materials do not produce their own magnetic field because the domains inside the material do not align with each other, and this will be explain shortly.

Why are some Ferromagnetic doesn¡¦t attract one another?

If the domains of the material do not align with each other like the diagram below left (a), they are unmagnetized material. The magnetic field inside the material cancels out with one another.

If the domains of the material do align with each other like the diagram above right (b), they are magnetized material. The magnetic field inside the material will not cancel out with one another.

Paramagnetic

Any materials that possess magnetization (i.e. attraction with other magnetized material) WITH an external magnetic field are paramagnetic. They have small and positive magnetic susceptibility. Aluminum and Platinum are examples of paramagnetic materials

Platinum Pt

Diamagnetic

Any materials that have very weak and negative susceptibility to magnetic fields are diamagnetic. Human (mostly), Copper and Gold are examples of diamagnetic materials.

Gold

Facts

l Negative magnetic susceptibility = repel against magnetic fields (diamagnetism)

l Positive susceptibility = attract to magnetic fields (para + ferromagnetism)

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