How does heat affect magnets?

Magnets are used in many different fields, such as manufacturing, in the automotive industry, in security systems and electronic devices, in everyday life and even planet Earth itself is a gigantic magnet, but how does heat affect magnets? It is an answer that we will get in this article.

To understand how heat affects magnets, it is necessary to look at the atomic structure of the elements that make up the magnet. Temperature affects magnetism by either strengthening or weakening the attractive strength of a magnet. A magnet subjected to heat experiences a reduction in its magnetic field as the particles inside the magnet move at an increasingly faster and more sporadic speed.

Heat affects the magnets because it confuses and misaligns the magnetic domains, causing magnetism to decrease. On the contrary, when the same magnet is exposed to low temperatures, its magnetic property improves and strength increases.

In addition to the resistance of the magnet, the ease with which it can be demagnetized also varies with temperature. Like the strength of the magnet, heat affects the magnets in terms of resistance to demagnetization, which generally decreases with increasing temperature. The only exception are ceramic (ferrite) magnets, which are easier to demagnetize at low temperature and more difficult to demagnetize at high temperature.

Different magnetic materials react differently with temperature. Alnico magnets have the best resistance stability, followed by SmCo, NdFeB and then ceramic. NdFeB magnets have the highest resistance to demagnetization (coercitivity), but experience the greatest change with temperature. Alnico magnets have the lowest resistance to demagnetization, but the smallest change achieved with temperature. Alnico has the highest operating temperature followed by SmCo, ceramic and then NdFeB.

But not everyone is aware of how a magnet affects its maximum usable temperature. This is especially important for NdFeB magnets, because they have the greatest change in resistance to demagnetization with temperature. As the length of the magnetized shaft increases, so does its resistance to demagnetization.

A verifiable experiment

It's a fact that heat affects magnets, a fact that makes them permeable. For example, the effect of temperature on neodymium magnets is one of the most interesting phenomena to observe and evaluate. Indeed, there is an experiment with magnets, which specifically explores how they react when exposed to extreme heat.

In principle, it is an experiment not suitable for children and, in addition, it must be carried out with the maximum safety measures and it will bring us as a result how heat affects the magnets. For this, we will need the following elements:

• A 100°C thermometer

• Plastic tweezers

• 2 bars of neodymium magnets

• Safety glasses and gloves

• Water

• Stove

• Bread

• Plastic container

• 100 clips

Heat affects the magnets in two simple steps. The first of them is a test of ambient temperature and for it the paper clips must be poured in a plastic container, to then submerge one of the magnets of bar of neodymium in the container of clips and to remove it, registering the collected number. The paper clips are then removed from the magnet and set aside.

When doing so with hot water, gloves and goggles should be worn. Heat about one-third of the cup of water in a small saucepan until it reaches 85°C or 100°C. At boiling point, the water should be near or within this temperature range and the thermometer is used to verify that the grade is appropriate.

Using the plastic clips, gently place the neodymium magnet in the water and leave it there for about 15 minutes. The magnet is then removed with the plastic clips and placed in the container with clips. Once there, you will see how many clips are collected.

The result will be obvious. The heated magnet will not lift the clips or, in any case, it will lift very few, depending on the temperature and the moment at which it was heated, which makes it evident that the heat directly affects the magnets.