"A magnet is a material or object that produces a magnetic field."
Materials that exhibit magnetic properties, including ferromagnetism, antiferromagnetism, and paramagnetism.
Basic concepts of magnetism: This topic covers the fundamental concepts of magnetism such as magnetic moment, magnetic field, magnetic dipole, etc.
Magnetic materials classification: The classification of magnetic materials is based on their magnetic behavior. The types of magnetic materials include diamagnetic, paramagnetic, ferromagnetic, ferrimagnetic, and antiferromagnetic materials.
Quantum theory of magnetism: This topic covers the quantum theory approach to magnetism, which includes spin models, exchange interactions, and spin Hamiltonians.
Magnetization and magnetic ordering: Magnetization refers to the extent to which a magnetic material is magnetized. Magnetic ordering refers to the arrangement of magnetic moments in a material.
Magnetic domains: Magnetic domains are regions in a magnetic material where the magnetic moments align in the same direction.
Spintronics: Spintronics is a field that studies the use of electron spin in electronic devices. This topic finds applications in fields such as data storage and processing.
Magnetic resonance: Magnetic resonance techniques such as nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) are widely used in the study of magnetic materials.
Magnetic hysteresis: Magnetic hysteresis refers to the property of a magnetic material where it retains a degree of magnetization even after the external magnetic field is removed.
Magnetic anisotropy: Magnetic anisotropy refers to the directional dependence of the magnetic properties of a material.
Magnetic imaging techniques: Techniques such as magnetic force microscopy (MFM) and magnetic resonance imaging (MRI) are used to visualize magnetic patterns and structures.
Synthesis and characterization of magnetic materials: This topic covers the methods used to synthesize magnetic materials and the characterization techniques used to study their magnetic properties.
Applications of magnetic materials: Finally, this topic covers the applications of magnetic materials in fields such as data storage, energy conversion, and biomedicine.
Diamagnetic materials: These materials have a weak magnetic moment which tends to oppose an applied magnetic field. They contain paired electrons with opposite spins which generate an opposing magnetic field.
Paramagnetic materials: These materials have a weak magnetic moment that aligns with an applied magnetic field. They contain unpaired electrons which generate a magnetic field that aligns with the applied field.
Ferromagnetic materials: These materials have a strong and permanent magnetic moment that aligns with an applied magnetic field. They contain magnetic domains that align in the same direction and generate a large magnetic field.
Antiferromagnetic materials: These materials have magnetic moments that cancel out each other due to their antiparallel alignment.
Ferrimagnetic materials: These materials have two types of magnetic moments (one stronger and one weaker) that are antiparallel, but not equal in magnitude, resulting in a net magnetic moment.
Superparamagnetic materials: These materials exhibit a magnetic moment that varies randomly due to thermal fluctuations.
Spin glasses: These are disordered magnetic materials and exhibit unique properties such as slow dynamics due to strong interactions between magnetic moments.
Magnetocaloric materials: These materials can experience a change in temperature when exposed to an external magnetic field.
Colossal magnetoresistive materials: These materials exhibit a large change in resistance when exposed to a magnetic field.
Magnetic shape memory alloys: These materials can change shape when exposed to a magnetic field.
"a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets."
"An object made from a material that is magnetized and creates its own persistent magnetic field."
"An everyday example is a refrigerator magnet used to hold notes on a refrigerator door."
"Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic)."
"These include the elements iron, nickel, and cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone."
"All other substances respond weakly to a magnetic field, by one of several other types of magnetism."
"Ferromagnetic materials can be divided into magnetically 'soft' materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically 'hard' materials, which do."
"Permanent magnets are made from 'hard' ferromagnetic materials such as alnico and ferrite."
"They are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize."
"The threshold depends on coercivity of the respective material."
"'Hard' materials have high coercivity."
"The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces."
"The local strength of magnetism in a material is measured by its magnetization."
"An electromagnet is made from a coil of wire that acts as a magnet when an electric current passes through it."
"An electromagnet [...] stops being a magnet when the current stops."
"The coil is wrapped around a core of 'soft' ferromagnetic material such as mild steel."
"It greatly enhances the magnetic field produced by the coil."
"A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field, whereas an electromagnet only acts as a magnet when an electric current is passing through it."
"The coil of wire acts as a magnet when an electric current passes through it."