Paramagnetism

Some things are weakly pulled by magnets.

This is called paramagnetism. It happens because of tiny parts called electrons. Some electrons are not paired up. These single electrons act like tiny magnets.

When a big magnet is near, these tiny magnets line up. This makes the whole thing move toward the big magnet. This pull is very soft. It stops when the big magnet is gone. Aluminum and oxygen are two things that do this. It is a neat way that things move!

Some materials are weakly pulled by magnets. This is called paramagnetism.

This happens because of tiny parts called electrons. In some atoms, electrons are not paired up. We call these unpaired electrons. These single electrons act like tiny magnets. They have a magnetic moment. This is a way to say they act like little poles.

When a big magnet is near, it creates a magnetic field. This field makes the tiny electron magnets line up. They point in the same direction as the field. This makes the whole material feel a small pull.

This pull is very weak. You might need a special tool to see it. Most materials like aluminum and oxygen do this. Oxygen is even a liquid that can float in a magnet!

Unlike a fridge magnet, these do not stay magnetic. When you take the big magnet away, the pull stops. This is because heat makes the tiny magnets jiggle. The jiggling makes them point in random ways again. This makes the total pull go back to zero.

Paramagnetism is a special way that some materials react to magnets. Most things we touch do not seem magnetic at all. However, some materials are weakly attracted to a magnetic field. This attraction happens because the material creates its own tiny magnetic field inside. This internal field points in the same direction as the outside field. This is different from diamagnetic materials, which are actually pushed away by magnets.

To understand how this works, we must look at tiny electrons. Electrons have a property called spin. Because of this spin, an unpaired electron acts like a tiny magnet. Most atoms have electrons that are paired up in sets. When electrons are paired, their tiny magnetic forces cancel each other out. But if an atom has unpaired electrons, it becomes paramagnetic. When you bring a large magnet nearby, these tiny electron magnets line up. They all point in the same direction as the external field.

Scientists have studied these magnetic forces for a long time. A famous rule called Curie's law helps explain how temperature affects this. This law shows that materials become more magnetic when they are colder. Heat causes the tiny electron magnets to jiggle around. This jiggling, or thermal motion, makes it harder for them to stay lined up. If you take the big magnet away, the magnetism disappears. The heat makes the spins point in random directions again.

Many different elements show this behavior in science. Aluminum is a common example of a paramagnetic metal. Other examples include titanium and oxygen. You can even see this with liquid oxygen. If you use a very strong magnet, the blue liquid oxygen will float between the poles.

Scientists use sensitive tools like a SQUID magnetometer to measure these small forces. These tools are much more precise than a regular handheld magnet.

Paramagnetism is a bit different from the magnets on your refrigerator. A refrigerator magnet is called a ferromagnet. Ferromagnets have a much stronger and permanent pull. They stay magnetic even when the outside field is gone. In paramagnets, the pull is very weak and temporary. Some metals also show a special version called Pauli paramagnetism. This happens when electrons move freely through a solid metal. Even in these cases, the effect is usually quite small.

Paramagnetism is a specific type of magnetism found in certain materials. These materials are weakly attracted to an externally applied magnetic field. When a field is present, the material forms an internal, induced magnetic field. This internal field points in the same direction as the external one. This behavior is the opposite of diamagnetism. Diamagnetic materials are actually repelled by magnetic fields. In diamagnetism, the induced field points in the opposite direction of the applied field.

The mechanism behind paramagnetism is found at the level of electrons. Every electron possesses a property called spin. Because of this spin, an unpaired electron acts like a tiny magnetic dipole. In most atoms, electrons exist in pairs within their atomic orbitals. When electrons are paired, their magnetic moments cancel each other out. However, atoms with incompletely filled orbitals often have unpaired electrons. These unpaired electrons create a permanent magnetic moment. When an external magnetic field is applied, it exerts a torque on these dipoles. This force causes the electron spins to align parallel to the field. This alignment creates a net attraction to the magnet.

There are different ways this magnetic response can manifest in matter. Most paramagnetic materials consist of localized electrons. In these cases, the magnetic moments come from individual atoms or molecules. A clear example is molecular oxygen. Even as a frozen solid, oxygen contains di-radical molecules. These molecules have unpaired spins in their p orbitals. Another type is known as Pauli paramagnetism. This occurs in conductive metals where electrons are delocalized. In these solids, electrons travel freely through the material. When a field is applied, the conduction band splits into spin-up and spin-down bands. This creates a small surplus of one spin type, resulting in a weak magnetic response.

Scientists use specific rules to describe how these materials behave. One important principle is Curie's law. This law states that magnetic susceptibility is inversely proportional to absolute temperature. In simpler terms, paramagnetic materials become more magnetic as they get colder. This happens because thermal motion causes random orientations of the spins. At high temperatures, this jiggling overcomes the magnetic alignment. As temperature decreases, the thermal agitation weakens. This allows the external field to align the spins more effectively. However, if the field is extremely strong or the temperature is extremely low, the material reaches saturation. At saturation, all dipoles are already aligned, so the magnetization cannot increase further.

Paramagnetism is much weaker than ferromagnetism. Ferromagnetic materials, like the iron in a refrigerator magnet, have a very strong and permanent attraction. They can retain magnetization even after the external field is removed. In contrast, paramagnets do not retain magnetization. Once the external field is gone, thermal motion randomizes the spin orientations again. The total magnetization drops to zero. The magnetic susceptibility for most paramagnets is quite small, typically between 10⁻⁳ and 10⁻⁵. Some special synthetic materials, called ferrofluids, can reach a much higher susceptibility of 10⁻¹.

Many different elements and compounds exhibit paramagnetic properties. Common examples include aluminum, titanium, and iron oxide (FeO). In the periodic table, elements with d or f electrons often show stronger magnetic effects. This is because these electrons are frequently more localized. For instance, lanthanide atoms can have very large magnetic moments. Gadolinium(III) can carry up to seven unpaired electrons. Because of these high moments, lanthanides are used in MRI technology. Other elements like platinum, tungsten, and magnesium also show measurable paramagnetic susceptibility. Platinum has a susceptibility of 26 × 10⁻⁵, while magnesium is much lower at 1.2 × 10⁻⁵.

Understanding paramagnetism helps scientists study the fundamental nature of matter. It connects the study of chemistry to quantum mechanics. The true origins of spin alignment can only be explained through quantum properties like angular momentum. Researchers use highly sensitive tools to detect these weak forces. One such tool is the SQUID magnetometer. This device allows for the precise measurement of the tiny magnetic moments produced by paramagnetic substances. By studying these effects, scientists gain insight into how electrons occupy energy bands and how temperature influences atomic structure.