Diamagnetic, Paramagnetic, and Ferromagnetic Materials
After reading this section you will be able to do the following:
Describe the sources of magnetic moments.
Identify the differences between diamagnetic, paramagnetic, and ferromagnetic materials.
When a material is placed within a magnetic field, the magnetic forces of the material’s electrons will be affected. This effect is known as Faraday’s Law of Magnetic Induction. However, materials can react quite differently to the presence of an external magnetic field. This reaction is dependent on a number of factors, such as the atomic and molecular structure of the material, and the net magnetic field associated with the atoms. The magnetic moments associated with atoms have three origins:
electron motion
change in motion caused by an external magnetic field
spin of the electrons
In most atoms, electrons occur in pairs. Electrons in a pair spin in opposite directions. So, when electrons are paired together, their opposite spins cause their magnetic fields to cancel each other. Therefore, no net magnetic field exists. Alternately, materials with some unpaired electrons will have a net magnetic field and will react more to an external field. Most materials can be classified as diamagnetic, paramagnetic, or ferromagnetic.
Diamagnetic, Paramagnetic, and Ferromagnetic Materials
Diamagnetic materials have a weak, negative susceptibility to magnetic fields. Diamagnetic materials are slightly repelled by a magnetic field and do not retain the magnetic properties when the external field is removed. In diamagnetic materials all the electrons are paired so there is no permanent net magnetic moment per atom. Diamagnetic properties arise from the realignment of the electron paths under the influence of an external magnetic field. Most elements
in the periodic table, including copper, silver, and gold, are diamagnetic.
Paramagnetic materials have a small, positive susceptibility to magnetic fields. These materials are slightly attracted by a magnetic field and do not retain the magnetic properties when the external field is removed. Paramagnetic properties are due to the presence of some unpaired electrons, and from the realignment of the electron paths caused by the external magnetic field. Paramagnetic materials include magnesium, molybdenum, lithium, and tantalum.
Ferromagnetic materials have a large, positive susceptibility to an external magnetic field. They exhibit a strong attraction to magnetic fields and are able to retain their magnetic properties after the external field has been removed. Ferromagnetic materials have some unpaired electrons so their atoms have a net magnetic moment. They get their strong magnetic properties due to the presence of magnetic domains. In these domains, large numbers of atom’s moments (1012 to 1015) are aligned parallel so that the magnetic force within the domain is strong. When a ferromagnetic material is in the unmagnetized state, the domains are nearly randomly organized and the net magnetic field for the part as a whole is zero. When a magnetizing force is applied, the domains become aligned to produce a strong magnetic field within the part. Iron, nickel, and cobalt are examples of ferromagnetic materials. Components with these materials are commonly inspected using the magnetic particle method.
Diamagnetic, paramagnetic, and ferromagnetic materials are three distinct categories of substances that exhibit different magnetic properties. These properties arise from the behavior of electrons within the material and their response to an external magnetic field.
Diamagnetic materials are characterized by their weak repulsion towards a magnetic field. When placed in a magnetic field, the individual atoms or molecules in a diamagnetic substance generate tiny opposing magnetic fields, causing the material as a whole to be repelled by the external field. This effect is very weak and typically only noticeable in the presence of strong magnetic fields. Diamagnetism is a universal property found in all materials to some extent, but it is usually overshadowed by other stronger magnetic effects.
Paramagnetic materials, on the other hand, exhibit a weak attraction towards a magnetic field. In contrast to diamagnetic substances, paramagnetic materials have unpaired electrons in their atomic or molecular orbitals. When exposed to an external magnetic field, these unpaired electrons align their spins with the field, resulting in a net magnetization of the material. However, this alignment is temporary and disappears when the external field is removed. The paramagnetic effect is generally much stronger than diamagnetism but weaker than ferromagnetism.
Ferromagnetic materials possess the strongest magnetic properties among these three categories. They exhibit a permanent magnetization even in the absence of an external magnetic field. Ferromagnetism arises from the alignment of electron spins within certain atomic or molecular structures called domains. Each domain acts like a tiny magnet, and when these domains are aligned, they create a macroscopic magnetization in the material. Unlike paramagnetism, ferromagnetism persists even after removing the external field due to interactions between neighboring atoms or molecules that maintain the alignment of domains.
The distinction between these three types of magnetism can be further understood by considering their temperature dependence. Diamagnetism and paramagnetism are generally temperature-independent, meaning their magnetic properties do not change significantly with temperature. However, ferromagnetic materials exhibit a critical temperature called the Curie temperature or Curie point. Above this temperature, the material loses its ferromagnetic properties and becomes paramagnetic. Below the Curie temperature, ferromagnetic substances can retain their magnetization even without an external field.
Review:
When a material is placed within a magnetic field, the magnetic forces of the material’s electrons will be affected. This effect is known as Faraday’s Law of Magnetic Induction.
Diamagnetic materials are slightly repelled by a magnetic field and do not retain the magnetic properties when the external field is removed.
Paramagnetic materials are slightly attracted by a magnetic field and do not retain the magnetic properties when the external field is removed.
Diamagnetic Paramagnetic Ferromagnetic Materials
Stainless Steel Case 800Kg Shuttering Magnet
Shuttering Holding Magnets – Magnetic Fixing System
Preparation Process of Sintered NdFeB Magnet
900kg Yellow Painted NdFeB Shuttering Magnet for Formwork Precast
1600kg Concrete Shuttering Magnet Boxes
600KG Shuttering Magnet NdFeB Form-work System
1000kg Shuttering Magnet Mould Box For Edge Formwork
Stainless Steel Magnetic Box Concrete Magnet 600Kgs
Precast Concrete Formwork Construction Shuttering Magnet 1500KGS
Neodymium Precast Shuttering Magnet White
Magnetic System Formwork Magnet Box 1000kgs