What is the Curie temperature of magnets?

The Curie temperature is known as the temperature at which the ferromagnetic element starts to lose its magnetism and becomes paramagnetic when this temperature is exceeded. In the case that the material is below the Curie temperature, magnetic materials are transformed into ferromagnetic ones. This temperature comes from Curie's law: it states that the susceptibility (the ability of a material to be magnetized by an external magnetic field) of a magnetic material is inversely proportional to the temperature.

As we can see in the graph, when a ferromagnetic element exceeds the Curie temperature, it becomes a paramagnetic element.

The person who determined the Curie temperature was the Frenchman in 1895 who discovered the laws that relate the alterations found in magnetic elements to the temperature at which they are found.

How can temperature affect the magnets?

The temperature at which is found in magnetic materials that have the presence of an external field, which contains ferromagnetic properties.

From the point of view of rocks and minerals, the ability of the element to maintain magnetism is at 570ºC; an example of minerals would be magnetite.

Low temperatures: If a magnet is at low temperatures the magnetism of the magnet will increase. When materials are in an environment with low temperatures, the magnetic atoms spontaneously realign themselves achieving a revival of ferromagnetism, antiferromagnetism, or ferromagnetism. In the case of minerals, the ability to retain magnetism is below the Curie point.

High temperatures:If the magnet is at high temperatures the magnetism of the magnet will be affected by the strength it possesses. This increase in temperature leads to conversion from ferromagnetism to paramagnetism, creating an increase in temperature, which is known as the Curie temperature.

What are the Curie temperatures of different materials?

Depending on the different types of magnets we will find different temperatures:

To know the loss or decrease of the magnetic properties of a material, when it reaches the Curie temperature, we will need the Curie Pendulum. This pendulum has a metal tip that is attracted to the magnet due to magnetic forces. On the other hand, to operate the pendulum we will need a candle, which will be the element that provides the heat.

The pendulum works as follows: when the element is heated by the candle and its temperature has increased, it will lose its magnetic properties, so it will move away. When the element is no longer attracted by the heat source, it will cool down, recover its properties, and will be attracted to the magnet again.

What substances are magnetic?

Magnetic substances are substances that have the ability to attract other magnetic elements or also known as magnets. The best known magnetic substances are:

- Iron

- Steel

- Cobalt

- Nickel

These substances, in addition to their combinations, have that property that allows them to attract or repel magnetic substances, with others. In the case that we try to join these substances with others that are not magnetic, that is to say, that they are not altered or affected by a magnetic field such as:

- Plastic

- Rubber

- Water

These non-magnetic substances will not be attracted.

Various elements are attracted by magnetic magnets, these materials can be divided into soft and hard materials. Soft materials are characterized by their ease of magnetization and demagnetization. Hard materials, on the other hand, have similar characteristics to permanent magnets, so, since they have a high BR, Hc, they have greater difficulty in activating or deactivating their magnetization.

How can magnetic substances be classified?

Magnetic substances can be classified depending on their properties, their behavior in the magnetic field, and magnetic permeability. Magnetic permeability is the capacity of different types of materials to attract or not metallic elements by means of magnetic fields.

All magnetic substances have in one way or another the presence of a magnetic field. The ability of a material to be magnetized by an external magnetic field is known as magnetic susceptibility.

How can we know the magnetic susceptibility?

The magnetic susceptibility is represented by Xm, we can get it by the relationship between the magnetization of the material and the intensity of the field that we want to apply.

Below, we can see the formula:

Magnetic susceptibility can be positive or negative, in case it is positive, we can classify it as a paramagnetic substance and ferromagnetic substance, on the other hand, if it is negative, we will classify it as a diamagnetic substance.

In this classification we find:

• Paramagnetic substances = Paramagnetic materials maintain their magnetism permanently. In addition, the magnetic susceptibility is small but positive. Paramagnetic substances contain electrons that are not paired.

• Diamagnetic substances = Materials that are composed of a diamagnetic substance repel magnetic fields, so as we have seen above, their magnetic susceptibility is negative.

• Ferromagnetic substances= Ferromagnetic substances are characterized by their high magnetic permeability.

Can we send magnets by post?

We can send magnets by postal mail, as long as we are very cautious since the magnetic field can transfer the packaging and the content of the packages that are close to it can be affected and damaged. In the same way, it can disrupt sorting systems and can be lost due to its attraction force being trapped in a metallic object. This is why if we need to send any magnetic element we must take care of the packaging.

Magnet shipments can be of two types:

• Air transport= Air transport is based on a type of transportation that allows parcels to be moved over long distances at a faster rate.
• Ground transport= Ground transport is usually used for short-distance shipments, being the most economical and practical transport as long as they are sent over short distances. shipped over short distances.
• Maritime transport= Maritime transport allows us to send large quantities of various dimensions at a very economical cost.

Regardless of the type of transport used, each country has its own rules.

How can we send a magnet by mail?

When sending magnets by postal mail you must take into account several factors, in addition to reducing the magnetic field. The factors we must take into account are:

1. The distribution of the magnets inside the package:

If we want to send more than one magnet, we must distribute them in such a way that half of the magnets are parallel to the other half, in other words, the poles must be in opposite directions to each other.

In the case that we only want to send two magnets, they cannot be placed parallel to each other but must be placed on a metal sheet, in the same way, one magnet must be placed with the north side facing the plate and the other with the south side. In this way, the magnets can be stylized and achieve a decrease in the strength of the magnetic field.

Another way to distribute the magnets so that they are not affected is: in the form of a circle so that the number of poles with a different directionalso achieves a neutralization of the field.

2. Distance required

As the distance between one magnet and another increase, the field strength decreases. We must also take into account the distance of the magnet from the envelope because if the envelope is very thin and the distance to the outside is small, this could affect the surrounding magnetic elements. This is why we can fill the space with materials that allow the isolation of the magnets, such as plastic.

In addition to these two factors mentioned above, we can also place an iron plate on each pole to protect the intensity of the field. Even so, before sending the package we must measure the magnetic force, by means of a Gaussmeter or Teslameter.