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Magnetism and Classification of Magnetic Materials

Magnets and magnetic fields produce a classic phenomenon that is known as Magnetism. Its origin is dependent on the orbital movements of the electrons of the element. It might be a surprising fact for you, but every matter has some magnetic property, and the only difference that is there is in respect to the amount of magnetism present. Moreover, the classification of the materials is done based on their magnetic properties.


Types of Magnetic Materials

Now, moving on to the classification of a magnet; it happens based on magnetism and goes as follows:

  1. Diamagnetism

  2. Paramagnetism

  3. Ferromagnetism

  4. Ferrimagnetism

  5. Antiferromagnetism.

The matters showing Paramagnetism and Diamagnetism are the ones that do not exhibit any magnetic interactions. However, the ones in the other three groups show a long-range magnetic order after certain temperature conditions.

Ferromagnetic and Diamagnetic materials are opposite to each other. When the former one shows magnetic behaviour, the latter one does not exhibit any such property.


What is Diamagnetism?

Now, how should we define diamagnetic materials?

A diamagnetic material is one that has a very low or minimal magnetic effect due to the absence of any unpaired electrons in them. 

Another way for explaining diamagnetic meaning is through Lenz’s law. It states that diamagnetic materials get induced dipoles in the presence of an external magnetic field, and this happens in such an order that the magnetic field and the induced dipoles repel each other.


What is Diamagnetic Material?

Moving on to the substances available globally, what are diamagnetic materials?

In 1845, Michael Faraday discovered diamagnets and the meaning of diamagnetic materials. Further, with the creation of the modern-day periodic table, experts commented and proved that most of the elements are Diamagnetic, like Gold, Silver, Copper, etc. These di-magnetic elements cover the majority of the table, and the other categories have a lesser number of elements. Moreover, semiconductors are the best diamagnetic materials. They also exhibit the diamagnetic field and this perfect diamagnetism in the superconductor is known as the Meissner effect.


Diamagnetic Properties

After understanding the diamagnetic definition well, let us move further with the properties. Properties of the diamagnetic materials are:

  1. The diamagnetic materials have all the paired electrons, and none of the electrons is the valence, resulting in the absence of atomic dipoles in these materials. This happens because the overall magnetic moment of each atom in the compound cancels out.

  2. In the presence of the magnetic field, there is a repulsion between the diamagnetic substance and the magnet.

  3. The field weakly repels the substances having diamagnetism; thus in the non-uniform field’s presence, these substances move from the stronger region of the magnetic field to the weaker one.

  4. In comparison to the magnetizing field, magnetization intensity is lower in the negative direction, and proportional.

  5. Diamagnetic materials have lower and negative magnetic susceptibility.

  6. The relative permeability is also a bit lower than unity.

  7. The materials that exhibit diamagnetism do not obey Curie’s Law. They are independent of the action of temperature.

  8. When suspending a rod of some material following diamagnetic definition in the uniform magnetic field, it comes to rest in the perpendicular direction with respect to the magnetic field. This happens as the magnetic field is highest at the poles.

  9. A diamagnetism-exhibiting liquid placed in a U-shaped tube gets depressed in the limb that is in the middle of the magnetic poles.

  10. The dipole moment of the di-magnetic substances is lower and in the opposite direction of the magnetic field H.

  11. When placing a diamagnetic liquid in a watch glass and then keeping the glass between two poles that stays closely, liquid accumulates at the sides of the glass. The liquid exhibits depression in the middle as the magnetic field is the strongest there.

  12. When placing a diamagnetic liquid in a watch glass and then keeping the glass between two poles that stay far apart, liquid accumulates in the middle of the glass. This reaction occurs because the magnetic field is weaker in the centre.


Fun Facts on Diamagnetic Substances:

Diamagnetic properties cause the objects to levitate. Unbelievable, right? But this is a proven fact! 

The reason is that the diamagnetic materials get magnetism only in the presence of the magnetic field, and these induced fields are opposite to the acting magnet. This is why they get utilized in many experiments for levitating the objects.

Moreover, even the Maglev train works with the help of this property of diamagnetism. Additionally, once a frog also got levitated in the presence of a strong magnetic field in an experiment.

FAQs on Diamagnetism

1. What is the Meissner Effect?

Whenever any substance is under the process of transition for becoming a superconductor, it starts losing the resistance to the electric current when cooled below the transition temperature (the temperature that is highly close to absolute zero). During the process, the substance starts expelling out the magnetic field, and this is known as the Meissner effect. 

The German physicists R. Ochsenfeld and W. Meissner discovered the Meissner effect in 1933 and unveiled that this effect is the common property of every superconductor.

2. What are the Superconductors and What is the Magnetic Susceptibility?

Superconductors are materials that exhibit diamagnetic properties. They have a volume susceptibility of Xv = -1, i.e. dimensionless. They are the perfect di-magnets and obey complete di-magnetic screening. For example, Aluminium, cuprates, etc.

The magnetic susceptibility of a material is the measurement of how much magnetic can it become after the application of some external magnetic field. In other words, this is the magnetization M’s ratio to H (the external magnetic field that is applied. The susceptibility of superconductors is generally around -1.

3. What is the history of the Magnetic field?

In the year 1269, the first research on the magnetic field commenced when a French scholar called, Petrus Peregrinus de Maricourt, traced out the magnetic field on the exterior of a spherical magnet. He did this with the help of iron needles. Maricourt saw that the consequent field lines crossed at 2 points and designated these points as poles. After this observation, Maricourt remarked that magnets always have North and South poles. Almost 3 centuries later, William Gilbert stated that our planet is also one big magnet. An English philosopher, John Mitchell stated in 1750, that magnetic poles repel and attract each other at all times.

A few years later, in 1785, Charles-Augustin de Coulomb experimentally demonstrated Earths’ magnetic field and finally, in the 19th century, French mathematician, Simeon Denis Poisson, created the 1st model of the magnetic field. By the 19th century, discoveries challenged the prior beliefs regarding the magnetic properties of the Earth.  In the year 1819, Danish physicist, Hans Christian Oersted,  discovered that an electric current creates a magnetic field around it. This opened many streams of study at the moment. In the year1825, André-Marie Ampère came up with a model of magnetism in which the force was stated, due to ever-flowing loops of current. This challenged the notion that dipoles of magnetic charge were responsible for it. In 1831, an English scientist named Faraday demonstrated that a constantly changing magnetic field induces an electric field and thus electromagnetic induction was discovered. Some years between 1861 and 1865, James Clerk Maxwell issued theories on electricity and magnetism which was known as Maxwell’s equation. Maxwell’s equations defined the relationship between magnetism and electricity.

4. How should one study magnetism and the chapter related to it?

Magnetism is a part of physics from which many questions are asked every year. Not only in School tests but competitive exams like JEE, NEET, etc also give a lot of weightage of marks to the magnetism topic. If a student is starting from scratch, they should first go through NCERT and keep their fundamentals right. Students can go through Vedantu's Youtube channel where they'll find various video lectures on magnetism and subtopics of magnetism. 

Students should make notes of formulas and points to remember when they watch the lecture or attend any class. This will help them to remember things when they sit to solve questions or during revision time. Students should also solve all the NCERT exercises and then can move on to the previous year's papers which will help them to go through questions patterns and exam patterns. Students can find study notes and a lot of FREE resources on Vedantu's official website. 

As physics is interconnected, the student should ensure that they pay attention in class and note down the important points told by the teacher as these could be asked as questions directly. Students need to practise more and more questions to have confidence in the topic of Magnetism. These are some of the ways the student can bring good marks in magnetism.

5. What are magnetic fields and what are the conditions for them to originate?

Magnetic field lines are lines that represent magnetic fields and define the direction of the magnetic force on the north monopole at a given position. The magnetic fields are always stronger and crowded around the poles of the magnet and the density of the magnetic lines displays the magnitude of the field. It becomes weak, as one goes away from the poles and the magnetic field lines become less thick. The magnetic field occurs only when a charge is in motion. The permanent magnets function based on the motion of electrons surrounding the nuclei. Not all materials can be converted or transformed into magnets. Some materials make much stronger magnets than others. Some conditions for magnetic field lines to occur are-

  • Atoms of a given element have numerous electrons and they are paired in a way that the general magnetic field cancels out to 0. 2 electrons paired in a way, where the magnetic field cancels out are said to own opposing spins. This states that if a material is tried to make into a magnet, it should have atoms that have 1 or more unpaired electrons having the same spin. For Example- Iron is an element that has 4 unpaired electrons and thus many magnets are made from iron.

  • If the atoms of a material are oriented randomly, the overall magnetic field cancels out. Then the fact of how many unpaired electrons the material holds doesn't matter. The material has to be stable enough, at room temperature to permit an overall best orientation to be established. If this property of magnetism stays permanently, they become a permanent magnet. These substances are also known as a ferromagnet.

  • Some of the materials become adequately well ordered to be magnets when they are presented with some amount of external magnetic field. The external field, lines all the electrons spins up, but the alignment disappears once the external field is taken out and these types of materials are called Paramagnetic substances.

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