Magnets, known as lodestones, are divided into natural (primarily magnetite) and artificial (metal alloys) categories. Artificial magnets are classified as "permanent" or "non-permanent," and further categorized as "hard" or "soft."
When exposed to a magnet's magnetic field, metal atoms align orderly, creating a net magnetic moment and magnetizing the metal. This interaction results in a strong electromagnetic force, causing the metal to be attracted to the magnet.
What properties of magnets?
Remanence (Br) | Remanence refers to the magnetic strength retained by a magnet after saturation and removal of external fields. Higher remanence means stronger magnetism and greater attraction. |
Coercivity (Hc) | Coercivity is the reverse field strength needed to demagnetize a saturated magnet. Higher coercivity means better resistance to external magnetic interference and increased stability. |
Maximum Energy Product (BHmax) | The maximum energy product is the peak magnetic energy density a magnet can achieve in air gap space, crucial for its energy storage capacity. Higher values indicate superior magnet performance. |
Which metallic materials can be stuck by magnets?
In addition to iron, a few other metals that a magnet or magnetic field can attract include cobalt, nickel, dysprosium, and gadolinium.
Iron (Fe)
- The most common magnetic material with strong magnetism.
- Iron's atomic magnetic moments tend to align in the same direction, leading to ferromagnetism.
- Iron loses its magnetism at about 770°C, known as the Curie temperature.
Cobalt (Co)
- Cobalt's magnetism is similar to iron, but it has a higher Curie temperature of 1150°C.
- Cobalt is one of the few metals that can retain magnetism at high temperatures.
Nickel (Ni)
- Nickel has weaker magnetic strength than iron and cobalt.
- It shows ferromagnetism at low temperatures and shifts to paramagnetism at high temperatures.
- It has a Curie temperature of about 358°C.
Dysprosium (Dy)
- It shows strong ferromagnetism at low temperatures, especially near absolute zero.
- Its Curie temperature is -188.15 ℃.
- Adding dysprosium to NdFeB magnets greatly boosts their coercivity, crucial for high-performance applications.
Gadolinium (Gd)
- It turns ferromagnetic below 16°C, its Curie point.
- It's the sole non-iron group metal exhibiting ferromagnetism close to room temperature.
What are the applications of magnetic properties?
- Electric motors
- Generators
- Magnetic storage devices
- Magnetic resonance imaging (MRI) machines
- Magnetic separation in mining and recycling
- Magnetic sensors in electronics and automotive systems
Studying magnetic materials enhances our understanding of magnetic phenomena, aiding in their optimal utilization and offering vital leads for new material and technology advancements.
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