#374 Superconductivity & Magnetism (again)

#374 Superconductivity & Magnetism (again)

#374 What is known about superconductivity?

Superconductivity is the phenomenon of zero electrical resistance and complete diamagnetism in certain materials when cooled below a critical temperature. It was first discovered in 1911. The theory of conventional superconductivity, which describes the behavior of simple metals like lead and aluminum, was developed by Bardeen, Cooper, and Schrieffer in 1957. More recently, the discovery of high-temperature superconductors has expanded the range of materials that exhibit superconductivity and challenged current understanding of the mechanism underlying the phenomenon. However, despite much research, a complete theory of high-temperature superconductivity remains elusive. Superconductivity has a wide range of practical applications, including in medical imaging, transportation, and energy production and distribution.

Why do materials superconduct?

Materials superconduct because the electrons in the material form Cooper pairs, which are pairs of electrons that behave as a single entity. In a superconductor, these pairs are able to move through the material with zero resistance because they are not scattered by lattice vibrations or impurities. This is in contrast to normal conductors, where electrical resistance arises from the collision of electrons with lattice vibrations and impurities. The formation of Cooper pairs requires a strong attractive interaction between electrons, which is facilitated by the lattice vibrations in the material. This interaction is strongest at low temperatures, which is why most superconductors must be cooled to low temperatures in order to exhibit superconductivity. The exact mechanisms that drive superconductivity and the conditions under which it occurs are still an active area of research in physics.

What cause magnetivity?

Magnetism is caused by the movement of electrons in an object. Electrons are tiny negatively charged particles that orbit the nucleus of an atom. When the electrons in an object are moving in the same direction, they create a magnetic field. The strength of the magnetic field depends on several factors, including the number of electrons moving in the same direction, the speed of their motion, and the direction of their movement.

There are two types of magnetism: diamagnetism and paramagnetism. Diamagnetic materials, such as copper, gold, and silver, have no permanent magnetic field and are weakly repelled by a magnetic field. Paramagnetic materials, such as iron, cobalt, and nickel, have a magnetic field and are attracted to a magnetic field. Ferromagnetic materials, such as iron and nickel, have a strong permanent magnetic field and are strongly attracted to a magnetic field.

Magnetism has many practical applications, including in electric motors, generators, and magnetic resonance imaging (MRI) in medicine.

Why does magnetism occur in permanent magnets?

Magnetism occurs in permanent magnets because the electrons in the magnet are aligned in such a way that they produce a persistent magnetic field. In a permanent magnet, the electrons are all spinning in the same direction and are not randomly oriented as they are in a non-magnetic material. This creates a net magnetic field that persists even when the magnet is removed from an external magnetic field.

The alignment of the electrons in a permanent magnet can be due to several factors, including the crystal structure of the material, the presence of magnetic impurities, and the process used to create the magnet. For example, many permanent magnets are made by heating a ferromagnetic material and exposing it to a strong magnetic field, which aligns the electrons in the material and causes it to become magnetized. The alignment of the electrons can also be affected by cooling the material and applying stress, which can cause the magnetic domains in the material to become more ordered and increase the overall magnetic field.

The magnetic field of a permanent magnet can be affected by other magnetic fields and temperature changes, so the magnetic properties of a permanent magnet can change over time. However, the magnet remains magnetized even when the magnetic field is no longer present, which is why it is called a "permanent" magnet.

Can permanent magnets at room temperature superconduct?

No, permanent magnets cannot superconduct at room temperature. Superconductivity is a phenomenon that occurs in certain materials when they are cooled below a critical temperature, and it is characterized by zero electrical resistance and complete diamagnetism. Permanent magnets, on the other hand, are materials that have a permanent magnetic field due to the alignment of electrons in the material. While permanent magnets may exhibit some diamagnetic behavior, they do not have zero electrical resistance and do not exhibit the other properties of superconductors.

In order for a material to exhibit superconductivity, it must meet certain requirements, such as having a suitable crystal structure and a strong attractive interaction between electrons. Most superconductors must be cooled to very low temperatures in order to exhibit superconductivity, while permanent magnets can exhibit their magnetic properties at room temperature.

Therefore, permanent magnets cannot be superconductors, and materials that are superconductors at low temperatures are not permanent magnets at room temperature.

What are all the methods for cooling materials below superconductivity critical temperature?

There are several methods for cooling materials below their critical temperature for superconductivity:

1. Liquid Helium Cooling: This is one of the most widely used methods for cooling superconductors. It involves immersing the superconductor in liquid helium, which has a boiling point of 4.2 K. Liquid helium is a good coolant because it is very cold, non-toxic, and has a low boiling point, making it easy to maintain the superconductor at a low temperature.
2. Cryocoolers: Cryocoolers are refrigeration units that use a mechanical cooling process to cool materials. They are often used to cool superconductors to temperatures just above the critical temperature for superconductivity.
3. Liquid Nitrogen Cooling: Liquid nitrogen has a boiling point of 77 K and is often used to cool superconductors because it is cheaper and more readily available than liquid helium. However, it is not as cold as liquid helium and is not as effective for cooling superconductors to the lowest temperatures.
4. Adiabatic Demagnetization Refrigeration (ADR): ADR is a cooling process that involves cooling a material by exposing it to a magnetic field and then removing the field. The process of removing the field causes the material to cool.
5. Dilution Refrigerators: Dilution refrigerators use a combination of a refrigerant and a diluent to cool materials. The refrigerant is used to cool the diluent, which in turn cools the material being studied. This method can achieve very low temperatures, making it useful for cooling superconductors.
6. Pulsed Tube Cooling: This method involves rapidly cooling a material by passing a gas through a pulsed tube. The gas is rapidly compressed and expanded, causing it to cool. The material is then cooled by contact with the gas.

These are the most common methods used for cooling materials below their critical temperature for superconductivity. The choice of cooling method depends on several factors, including the type of superconductor, the desired temperature, and the availability of cooling resources.

From <https://chat.openai.com/chat>