Magnetic Properties of Ceramic Minerals

AKSA MAGNET
Jan 15
3 min read

Aksa Magnet – Magnetic Separation

In our previous blog post, we provided a general introduction to magnetic minerals used in the ceramic industry and discussed the problems these minerals may cause in ceramic applications when magnetic separation is not applied. In this article, we will examine in more detail the different magnetic properties that minerals may exhibit.

Magnetic Properties of Ceramic Minerals

Source of Magnetic Properties

The factor that determines whether a mineral has magnetic properties is the electrons of the atoms or ions it contains. According to the principles of wave mechanics, as an electron moves in a closed orbit around the nucleus, it behaves like a wave and forms a current. This moving current generates a magnetic field.

When a crystal is placed in an external and non-uniform magnetic field, a force arises that attempts to align the magnetic fields of the atoms, creating a magnetic moment throughout the entire crystal. Magnetic susceptibility (χ) is the ratio between the induced magnetic moment (M) and the strength of the applied external magnetic field (H):

χ = M / H

Diamagnetism and Paramagnetism

Diamagnetic minerals have a negative χ value and are slightly repelled by a magnetic field. Paramagnetic minerals, on the other hand, have a positive χ value and are weakly attracted by a magnetic field.

Diamagnetism is related to the spatial distribution of electrons, whereas paramagnetism is associated with the spin motion of electrons. All atoms exhibit diamagnetic behavior. However, if an atom has incomplete electron shells (as in transition elements) or an odd number of electrons, the imbalance in electron spins causes the paramagnetic effect to dominate over the diamagnetic effect. In metals, paramagnetic behavior may also occur due to the presence of freely moving conduction electrons.

Such magnetic behaviors are generally considered in the context of crystals, because the internal structure of a crystal modifies magnetic effects. In crystals, electronic energy levels are split into different levels, and the total magnetic susceptibility depends on how electrons are distributed among these levels. Therefore, in complex compounds, it is generally not possible to predict magnetic properties in advance.

Mineral structures containing iron are generally paramagnetic. However, there are also some paramagnetic minerals that do not contain iron. As long as there is a sufficient difference in magnetic susceptibility, these minerals can be separated using high-intensity magnetic separators.

Bismuth can be given as an example of a diamagnetic mineral. Paramagnetic minerals are more common, and minerals such as hematite and biotite mica are frequently found in ceramic raw materials.

Ferromagnetism

Ferromagnetic minerals possess their own magnetic moments even when no external magnetic field is applied. These minerals can be permanently magnetized and are strongly attracted even by a weak magnetic field.

Ferromagnetic materials maintain a permanent alignment of the magnetic moments of their electrons due to interactions between neighboring atoms at room temperature, even under non-magnetic conditions.

Iron, cobalt, nickel, and minerals such as pyrite are typical examples of ferromagnetic materials.

Antiferromagnetism and Ferrimagnetism

In some crystals, specific alignment patterns of electrons give rise to antiferromagnetic or ferrimagnetic effects.

Antiferromagnetism

In antiferromagnetic minerals, adjacent atoms have spins aligned parallel but in opposite directions. This alignment is referred to as antiparallel spins. Since the two magnetic moments completely cancel each other out, such minerals do not exhibit a permanent magnetic moment.

Antiferromagnetism can be observed in oxides such as nickel oxide and in metals such as chromium.

Ferrimagnetism

In ferrimagnetic minerals, the magnetic moments resulting from antiparallel electron alignment are not equal, resulting in a net magnetic moment. Magnetite is a typical example of a ferrimagnetic mineral.

Magnetic Particles in Ceramics

Magnetic particles can cause serious problems for ceramic manufacturers. The presence of such contaminants in ceramic materials can negatively affect product quality. Fortunately, through magnetic separation methods, these particles can be effectively removed, preserving the integrity of ceramic products.

In our next blog post, we will discuss the problems caused by magnetic metal contamination in ceramic processing operations and explain how magnetic separation can solve these issues.

For more information on the removal of magnetic particles and the separation of different magnetic properties in the ceramic industry and many other sectors, you may contact Aksa Magnet.