Metals can broadly be classified as magnetic and non-magnetic, depending on the magnetic field generated around them.
So, which metals are non-magnetic? And how can you identify them?
Metals such as aluminum, copper, titanium, bismuth, lithium, lead, brass, and bronze are considered non-magnetic metals because they do not develop any significant repulsive or attractive force when subjected to a magnetic field. This makes them suitable for applications, such as MRI machines, that develop a strong magnetic field.
This article discusses non-magnetic metals in detail and sheds some light on the factors that make a metal magnetic.
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List of Non-magnetic Metals with their Applications
Compared to magnetic metals, non-magnetic metals are large in number. Transition metals like copper, silver, and gold, to name a few, are non-magnetic metals.
The following tables list a few non-magnetic metals, their properties, and their applications.
|Gold||Good corrosive resistance, low electrical resistivity, Malleable, Ductile||Used in computers, jewelry, EEG electrodes, and teeth fillings.|
|Copper||Excellent conductor of heat and electricity and good corrosion resistance||Utensils, shake flashlights, sub-sea applications,|
|Silver||High electrical conductivity, thermal conductivity, reflectivity, and good corrosion resistance||Solar Panels, Ornaments, and capacitors in medical equipment|
|Bismuth||High electrical resistance when subjected to a magnetic field.||Soldering applications, bullets|
|Lithium||High specific heat, High thermal conductivity, low-density||Non-magnetic batteries|
|Aluminum||High thermal conductivity, lightweight, good corrosion resistance||Marine applications, military, Electronic casings, Electrical transmission lines|
|Titanium||High strength-to-density ratio and excellent corrosion resistance||Tools, missiles, microwave connectors, and ships|
|Platinum||Good corrosion resistance, soft and malleable, high-density||Electrodes, high-density hard disk drives, and optical storage systems.|
Gold is a soft, ductile metal that has good corrosion resistance. Its low electrical resistivity and non-magnetic properties make it an ideal metal for making EEG electrodes (to measure brain signals).
Apart from being non-magnetic, copper is said to have high thermal conductivity, electrical conductivity, and good corrosion resistance.
The non-magnetic property of copper is utilized in mechanical shake flashlights and sub-sea applications like seawater pipings, couplings, etc.
Resistance to fouling makes copper suitable for applications of long periods of inactivity, like submerged testing devices.
Copper alloys, such as brass, also present non-magnetic properties, making them suitable for similar applications.
Silver has good thermal conductivity, electrical conductivity, and corrosion resistance.
In addition to these properties, the non-magnetic nature of silver makes this metal an ideal choice for making capacitors used in medical devices like MRI (magnetic resonance imaging) and NMR (nuclear magnetic resonance scanners).
Low density and high resistance to electricity in the vicinity of an external magnetic field make the bismuth chosen for soldering purposes.
Lithium has high specific heat, high thermal conductivity, and low density, making them suitable for electrical applications.
One of the most popular applications of lithium can be found in the form of lithium-ion (Li-on) batteries.
The non-magnetic nature of lithium makes it suitable for electronic gadgets such as smartphones, which otherwise can experience interference in the presence of an external magnetic field.
Aluminum, a lightweight metal, has high thermal and electric conductivity. Apart from these qualities, it has good corrosive resistance and is non-magnetic.
The non-magnetic property of aluminum helps build electronic casings and marine structures and develop military devices that are not susceptible to the magnetic field.
The high strength-to-density ratio and non-magnetic nature of titanium make it an ideal metal to develop tools that are used while working on magnetic devices like MRI equipment or highly reliable testing devices.
Apart from this, titanium has found wide applications in the field of spacecraft, shipbuilding, and developing missiles.
Platinum is a highly dense, ductile, malleable, and corrosion-resistant material. Its non-magnetic property is harnessed in making pacemakers and catalytic converters.
What are Non-Magnetic Metals?
Metals that exhibit weak magnetic responses are categorized as non-magnetic metals. In addition, these metals exhibit a low relative permeability.
The measure of magnetization is termed permeability. It is a property that explains the material's response to the magnetic field.
Magnetism is of three types: Ferromagnetic, Paramagnetic, and Diamagnetic.
Paramagnetic and diamagnetic metals are categorized as non-magnetic metals for their weak magnetic nature.
|Type of Metal||Nature||Magnetic Behavior|
|Diamagnetic||Non-magnetic||Weak repulsive magnetic field is induced|
|Paramagnetic||Non-magnetic||Weak attractive magnetic field is induced|
|Ferromagnetic||Magnetic||Strong attractive magnetic field is induced|
When placed in an external field, the diamagnetic metals have an induced magnetic field of relatively low magnitude.
This induced magnetic field is repulsive in nature as the electron's spin is opposite to the direction of the external field.
Therefore, diamagnetic metals can be characterized by their repulsive behavior, whereas paramagnetic and ferromagnetic metals are attracted toward the field.
When placed in an external field, the paramagnetic metals experience a weak induced magnetic field, and the electron's spin is found to be in the direction of the external field.
As a result, these metals are attracted toward the source of the magnetic field.
When placed in an external field, the ferromagnetic metals experience a very strong induced magnetic field, and the electron's spin is in the direction of the external field.
This inducted field is maintained even at normal temperatures. The demagnetization often involves heating them above the Curie temperature.
Compounds made of multiple elements are termed ferrimagnetic and anti-ferromagnetic.
Ferrimagnetic and anti-ferromagnetic metals have their electron spin opposite to the external magnetic field but vary in the amount of induced magnetic field.
In practice, due to crystal defects, the induced magnetic field in anti-ferromagnetic metals does not exactly oppose the external field. Thus, these materials display certain magnetic responses.
Types of Magnetization
The magnetization of a metal can be classified as natural or man-made.
The relative motion of electrons in an atom determines whether the material has magnetic properties or not.
Based on the electron spin, the magnetic property is imparted at the atomic level and transmitted to the crystalline level.
It is at the crystalline level that many magnetic or non-magnetic metals are classified. For example, iron exists in both body-centered and face-centered cubic structures.
The body-centered structure of iron is generally found at room temperature, inducing a ferromagnetic property to the metal.
In contrast, it becomes face-centered and paramagnetic at higher temperatures (above Curie temperature), losing its magnetic properties.
Silver, gold, and platinum are face-centered crystal structures with weak magnetic properties.
Whereas, metals such as iron, cobalt, nickel, and certain rare earth metals are naturally ferromagnetic at room temperature, and are thus classified as natural magnetic metals.
However, the properties of these metals can be altered during manufacturing or heat treatment processes, depending on the temperature.
Generally, permanent magnets are termed metals that can hold magnetic properties for long durations.
Current and magnetic fields are interconnected. Current can induce a magnetic field in the metal, and the same is the other way around.
When current is passed through a wire-wound iron core, a magnetic field is generated around the coil, thus magnetizing the core.
Thus the magnetized core is called an electromagnet.
Electromagnets use current to magnetize. Once the current is off, it loses its magnetic power. But, by varying the amount of current supplied, varying amounts of magnetization can be developed.
By reversing the direction of the current flow, the position of the poles can be reversed.
A few examples of electromagnets are earphones, loudspeakers, electronic doorbells, etc.
The traditional DIY technique of inducing forced magnetism involves either rubbing weakly magnetic metals against a strong magnet or hitting the metal with a hammer.
These tricks work because the electrons get redistributed in the metal to temporarily create a magnetic moment. But, these effects are temporary and do not last long.
Creating a magnetic metal the DIY way for commercial applications is not useful. Scientists worldwide are trying new techniques to create a longer-lasting magnet.
There are techniques ranging from using additives to using polarized light to alter the material properties. All this involves altering the behavior of electrons in the metals.
Magnetic vs. Non-magnetic Metals
|Magnetic Metals||Non-magnetic Metals|
|Exhibits attraction and repulsive nature and creates a magnetic field.||Do not have attraction and repulsive nature. |
Can exhibit a very weak magnetic field.
|Have lower coercivity.||Higher coercivity.|
|Electron spins are aligned with the direction of an external magnetic field||Electron spins cancel out each other.|
|Easily detected by metal detectors as they respond to an external magnetic field||Not easily detected by metal detectors unless they have good electrical conductivity and magnetic permeability.|
|Not suitable for electrical wiring as they produce a magnetic field||Suitable for electrical insulations and wiring.|
|Iron, cobalt, nickel, and their alloys are some examples.||Copper, titanium, and aluminum are some examples.|
Based on the Nature of Metal
Magnetic materials exhibit the nature of attracting and repelling other materials in the presence of a magnetic field, whereas a non-magnetic material remains unresponsive.
Based on the Coercivity of Metal
Coercivity is the property of a material that tells how strong the magnetic field should be to magnetize/demagnetize them.
Magnetic materials exhibit lower coercivity compared to non-magnetic materials, which possess high coercivity.
Based on the Electron spins
In magnetic materials, the electron spins align in the direction of the magnetic field, whereas for a non-magnetic material, the electron spins align in such a way that their spins cancel out each other.
Based on the Applications of Metals
Based on their utility, magnetic and non-magnetic materials have different applications.
Metal detectors easily detect magnetic materials and thus have wide applications in the military and industries.
Non-magnetic materials are widely used in electrical wiring and for insulation purposes.
Non-magnetic metals are generally used for applications that are subjected to high temperature, corrosive, and magnetic environments.
At higher temperatures, the non-magnetic metals retain their crystalline structure, thereby facilitating their use. For example, paramagnetic metal bauxite is used in blast furnaces.
Using titanium as a safety tool shows its exemplary durability to withstand magnetic forces.
Apart from non-magnetic metals, you can also opt for other non-magnetic materials like rubber, plastic, wood, etc., for applications where high strength or conductivity is not generally required.
Frequently Asked Questions (FAQ)
Can non-magnetic metals be magnetized?
Yes, non-magnetic metals can be magnetized by rubbing the metal against a strong magnet or by striking the metal with a hammer.
Can magnetic metals lose their magnetic properties?
Yes, magnetic metals heated to a temperature above curie temperature lose their magnetic property.
How does hammering affect the magnetic property?
Hammering a material alters the orientation of the dipoles of the material, thereby altering their magnetic propeties.