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Lecture

Hard Magnets: Materials, critical elements, Sect. 4.6&4.7

In course

MSE-432: Introduction to magnetic materials in modern technologies

Interactive course addressing bulk and thin-film magnetic materials that provide application-specific functionalities in different modern technologies such as e.g. wind energy harvesting, electric article surveillance, spintronics, sensing, and data storag ...

Description

This lecture covers the fundamental concepts of hard magnets, including the importance of energy product, coercive field, and anisotropy. Specific examples such as Nd-Fe-B and SmCo are discussed, highlighting their unique characteristics and production methods. The lecture also delves into the performance enhancement by Dy and the challenges in the magnet production and supply chain, emphasizing the significance of rare earth elements. Various applications of hard magnets, such as in wind energy and MRI, are explored, showcasing their crucial role in modern technologies.

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Instructor

Dirk Grundler

Official source

Ontological neighbourhood

Physics

Condensed matter physics: Phase transitions

Related concepts (14)

Neodymium magnet

A neodymium magnet (also known as NdFeB, NIB or Neo magnet) is a permanent magnet made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. Developed independently in 1984 by General Motors and Sumitomo Special Metals, neodymium magnets are the strongest type of permanent magnet available commercially. Neodymium magnet are the most widely used type of rare-earth magnet. NdFeB magnets can be classified as sintered or bonded, depending on the manufacturing process used.

Rare-earth magnet

A rare-earth magnet is a strong permanent magnet made from alloys of rare-earth elements. Developed in the 1970s and 1980s, rare-earth magnets are the strongest type of permanent magnets made, producing significantly stronger magnetic fields than other types such as ferrite or alnico magnets. The magnetic field typically produced by rare-earth magnets can exceed 1.2 teslas, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla. There are two types: neodymium magnets and samarium–cobalt magnets.

Coercivity

Coercivity, also called the magnetic coercivity, coercive field or coercive force, is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized. Coercivity is usually measured in oersted or ampere/meter units and is denoted HC. An analogous property in electrical engineering and materials science, electric coercivity, is the ability of a ferroelectric material to withstand an external electric field without becoming depolarized.

Magnet

A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets. A permanent magnet is 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.

Ferrite (magnet)

A ferrite is a ceramic material made by mixing and firing iron(III) oxide (, rust) with one or more additional metallic elements, such as strontium, barium, manganese, nickel, and zinc. They are ferrimagnetic, meaning they are attracted by magnetic fields and can be magnetized to become permanent magnets. Unlike other ferromagnetic materials, most ferrites are not electrically conductive, making them useful in applications like magnetic cores for transformers to suppress eddy currents.

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