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How do magnets demagnetize?

Author Archives: amartin

  1. How do magnets demagnetize?

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    Before we explain how magnets demagnetize – lose their magnetism, it may be helpful to note:

    Permanent magnets are made of elements known as ferromagnetic materials by exposing them to a magnetic field using electric current. Using a magnetizing fixture that directs current through the non-magnetized part, electron spins in these metals are lined up, or polarized, making the material magnetic.

     

    Magnets can lose their magnetism, or demagnetize, in a few different ways:

    demagnetization by heatHeat: When exposed to high temperatures, the tiny magnetic regions within the material, called magnetic domains, vibrate more energetically. This vibration disrupts the alignment of these domains, weakening or even destroying the magnet’s overall magnetic field. The specific temperature at which this happens, called the Curie temperature, varies depending on the material the magnet is made of.

    Cold: Some magnet materials lose their ability to resist demagnetization at cold temperatures. Ceramic/Hard Ferrite materials are at risk at temperatures below -40°C (-40°F) and Neodymium Iron Boron has problems below -138°C (-216°F). Neither Alnico nor Samarium Cobalt experience this effect and they can be used down to near Absolute Zero, -273°C (-460°F)

    Strong magnetic fields: Exposing a magnet to a strong magnetic field in the opposite direction of its own magnetism can also disrupt the alignment of its internal domains. This can happen accidentally, for example, if you bring a strong magnet close to another magnet. Degaussing, a technique used to intentionally remove magnetism from objects, also works on this principle by applying a strong, alternating magnetic field.

    demagnetization over time Time: While less common, even at room temperature, thermal vibrations can very slowly misalign the magnetic domains, causing a gradual weakening of the magnet’s field over extended periods, typically over decades. This process is much slower than the other methods mentioned above.

    It’s important to note that demagnetization can be reversible or irreversible depending on the severity of the cause and the type of magnet. In some cases, simply removing the magnet from the heat source or the strong magnetic field can allow the domains to realign and regain some or all of its magnetism. However, in other cases, the damage might be permanent.

  2. Women in STEM Magnetism

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    Throughout history, women have made significant contributions in fields ranging from economics and civil engineering to yes, you guessed it, science. For example, Ada Lovelace wrote what is considered the world’s first computer code. Chemist Katharin Blodgett is credited with creating the world’s first clear glass. And on a hot, sunny day, you can thank Nancy Johnson for inventing the very first ice cream maker.

    Since magnets play a major part in many scientific discoveries and innovations, and since we’re all about magnets, we’re highlighting a few of the many women in STEM magnetism, just in time for Women’s History Month.

    Introducing…

    Dr. Shirley Ann Jackson

    Dr. Shirley Ann JacksonEvery time you use your smart phone or play on your iPad, you can thank Dr. Shirley Ann Jackson. One of the first two Black American women to obtain a doctorate degree in physics in the United States, theoretical physicist Dr. Jackson’s work helped create the materials used in today’s computers, smart phones, and other electronics.

    To understand Dr. Jackson’s work, you first need to understand electrons and semiconductors. You probably know that everything around you is made of molecules, and that molecules are made of atoms, and that inside atoms there are protons, neutrons, and electrons, the tiny, charged particles whose electrical charges line up to create a magnetic field.

    Just like its name sounds, a semiconductor is a special material that semi – or somewhat – conducts an electrical current. Working in the top physics labs in the world, Dr. Jackson explored different ways to control electrons inside semiconductors and her discoveries made things like touch tone phones, caller ID, and call waiting possible.

    Her contributions to science and technology were so important that she was named the head of the Nuclear Regulatory Commission, president of Rensselaer Polytechnic Institute, and served on Obama’s President’s Council of Advisors on Science and Technology.

    Donna Elbert

    American applied mathematician, Donna Elbert, is proof that you don’t necessarily need advanced training to dive into deep problems.

    With no formal training in math or even a university degree, Elbert spent more than 30 years conducting advanced analytical physics computations by hand for renowned astrophysicist Subramanyan Chadrasekhar. Serving as a human computer, Elbert worked side by side with Chandrasekhar, researching the magnetic fields of planets and it was she who recognized and calculated the consequences of the balance between planetary rotation, convection, and magnetic fields.

    Chadrasekhar credited Elbert’s finding in his textbook, published in the 1960’s, but it is only recently that scientists and mathematicians have the computing power to calculate the scenarios Elbert observed. Her observations have been dubbed the Elbert range and physicists are still working through its ramifications today.

    Chien-Shiung Wu

    You may have seen the movie Oppenheimer, about the man who led the building of the atomic bomb as part of The Manhattan Project. What the movie didn’t tell you is that a Chinese American scientist named Chien-Shiung Wu also played a major part in The Manhattan Project.

    Born in China in 1912, Wu taught herself algebra, geometry, and trigonometry and studied math and physics in college in China before moving to America to earn her Ph.D. physics at U.C. Berkeley. This is where she eventually presented her thesis on bremsstrahlung, a German term for the electromagnetic radiation that is produced by a sudden slowing of charged particles. Her work was so impressive that she was asked to join The Manhattan Project, where she solved a major nuclear reactor problem and built a Geiger counter designed to detect nuclear radiation levels.

    Wu’s contributions to the study of beta decay are still referenced by nuclear physicists today. Wu’s intelligence and dedication to her field earned her positions that were not available to most women at the time; she is thought to be the only Chinese person to have worked on The Manhattan Project. Her groundbreaking and barrier breaking work earned her many awards, including the Wolf Prize in Physics, the Comstock Prize in Physics, and the National Medal of Science for Physical Science.

    Myriam Sarachik

    Belgian-born Myriam Sarachik spent her early years in a concentration camp in France before escaping to Cuba, where her family sought refuge while seeking entry into the United States. Sarachik studied physics at Barnard and later at Columbia, where she researched the reductive powers of Type-I superconducting films on magnetic fields. She went on to serve as a full professor at City College of New York.

    Sarachik studied the effects of low temperatures on condensed matter properties, conducting some of her research near temperatures of absolute zero. She has been published extensively in professional journals on her work in superconductivity, disordered metallic alloys, metal-insulator transitions in doped semiconductors, hopping transport in solids, properties of strongly interacting electrons in two dimensions, and spin dynamics in molecular magnets.

    The recipient of countless awards and fellowships, Sarachik served as President of the American Physical Society and on the council of the National Academy of Sciences. She was also an avid defender of the human rights of scientists.

    Rosalind Franklin

    Rosalind FranklinA baby with two parents with green eyes will always have green eyes, right? These findings – and other, more important genetic information – can be predicted thanks to Rosalind Franklin, the British chemist who discovered the molecular structure of deoxyribonucleic acid, aka DNA.

    Franklin used X-ray diffraction to reveal this structure of complex molecules, a process that uses a crystal to diffract the X-ray wavelengths and reveal the geometry of a molecule. In addition to uncovering the structure of DNA, Franklin’s process contributed to our understanding of the structure of other complex molecules, including the molecules that make up magnetic materials as well as the first ever detailed molecular structure of a virus.

    There’s also a bit of drama surrounding Franklin’s DNA discovery. Some people think that James Watson and Francis Crick, the two men credited for discovering the DNA double helix, or twisted structure of DNA, only made the discovery after being shown Franklin’s X-ray image – without her permission. As the old joke, which is not so funny, goes, “What did Watson and Crick discover in 1953? Franklin’s data!”

    This Women’s History Month we honor these women, and so many others, who have worked tirelessly to break the gender barriers that existed in science in their day and make these meaningful contributions. Thanks to their work, girls and women today are free to work in any field they like – and to receive credit for their discoveries.

  3. What Happens When Magnets Get Cold?

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    Cold weather is great for sipping cocoa by the fire, watching college football, and making snow angels. But how do cold temps affect magnets? Luckily, most magnets actually become stronger and more resistant to demagnetization in cold weather.

    • Strength: In most cases, cold temperatures increase the strength of a magnet’s magnetic field. This is because the atoms in the magnet move slower and vibrate less, allowing them to align more consistently and generate a stronger field.
    • Demagnetization: Cold can also affect how easily a magnet can be demagnetized. Generally, colder temperatures make most magnets more resistant to demagnetization. Ceramic (Ferrite) magnets are the exception here – they become easier to demagnetize when cold.

    Variations depending on material:

    • Neodymium magnets: These powerful magnets will perform well at temperatures as low as -130°C. In fact, their magnetism strengthens in the cold until this point Once you move into extremely frigid conditions (below -135°C), the field will begin to diminish. At the boiling point of liquid nitrogen (‑196°C), a neodymium magnet’s field strength will decrease by 85-90%. At this temperature, the molecules in the magnet fall out of alignment. However, when the temperature rises, the magnet will return to normal performance.  The change in magnetic output is reversible; that is, no permanent loss of magnetic strength occurs.
    • Ferrite (Ceramic) magnets: These common magnets are generally less powerful and more susceptible to demagnetization. While cold temps initially strengthen their magnetism, they can lose their strength at temps below -60°C.
    • Flexible magnets: Flexible magnet strips and sheets can become stiffer or more brittle at extreme temperatures. Check the manufacturer’s specifications for your specific magnets.
    • Alnico and Samarium Cobalt magnets: These durable magnets have high thermal stability and are less affected by temperature changes than other types of magnets. These magnets will continue to get stronger as the temperature decreases, all the way to near Absolute Zero (-459°F or -273°C).
    • Electromagnets:  Colder temperatures decrease the resistance of the wire in electromagnets, allowing more current to flow and strengthening their magnetic fields.

    Important note: While cold generally strengthens most magnets, extreme temperature changes can be detrimental. Moving rapidly from very cold to very hot temps can cause magnets to crack or break.

    Try This Experiment to See the Impact of Cold on Magnets!

    It won’t be a dramatic difference, but if you’re curious you can monitor the change in a magnet’s strength with this simple experiment.

    1. Starting at room temperature, drop a neodymium magnet into a bowl of paper clips and count how many become attached.
    2. Next, fill the bowl with water (leave the paperclips in the bowl) and put it in the freezer until the temperature of the water falls near freezing, but isn’t frozen (32°F).
    3. Now drop the magnet into the water and put the bowl back in the freezer for 15 minutes, removing the bowl from the freezer just before the water freezes.
    4. Remove the magnet from the bowl and count the number of attached paper clips. Compare this number to the number of clips that attached to the magnet at room temperature.

    Now you know what happens when your magnet or magnet application is exposed to cold temperatures. If you have questions about your specific magnet scenario, please feel free to reach out to our experts – we love to talk magnets!

    We hope this clarifies how cold affects magnets! If you have any further questions, contact us.

  4. Permanent Magnets in EVs

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    Permanent magnets play a critical role in electric vehicles (EVs). They are used in the electric motors that power the wheels, as well as in other components such as the power steering and air conditioning system.

    Permanent magnets create a strong magnetic field that does not require electricity to maintain. This makes them ideal for use in EVs, as they can help to improve the efficiency of the electric motor and extend the range of the vehicle.

    The most common type of permanent magnet used in EVs is neodymium iron boron (NdFeB). NdFeB magnets are very strong magnetically enabling miniaturization, making them ideal for use in applications where space and weight are at a premium.

    Here are some of the specific benefits of using permanent magnets in EVs:

    • Improved efficiency: Permanent magnet motors are more efficient than other types of electric motors, such as induction motors. This means that they can convert more of the electrical energy from the battery into mechanical energy to propel the vehicle.
    • Higher torque density: Permanent magnet motors have a higher torque density than other types of electric motors. This means that they can produce more torque for a given weight and size. This is important for EVs, as it allows them to accelerate quickly and climb hills easily.
    • Reduced heat generation: Permanent magnet motors generate less heat than other types of electric motors. This is because they do not require electricity to maintain their magnetic field. This helps to extend the lifespan of the motor and improve the overall efficiency of the EV.

    Overall, permanent magnets play a vital role in the performance and efficiency of electric vehicles. They are essential components in the electric motors that power the wheels, and they are also used in other important components such as the power steering and air conditioning system.

    Further reading:

  5. New Lower Cost Neodymium Magnet Option

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    Background

    You may have heard there’s a new, lower-cost Neodymium Iron Boron magnet option. This new option replaces some of the Neodymium with Cerium, which helps to reduce the cost of the magnet.

    A Bit of Neodymium History… Er, Science… Nope, History

    The popular Neodymium magnets are made up of a variety of materials, mostly Neodymium, Iron and Boron. They can also contain elements such as Dysprosium, Praseodymium, Cobalt, and a few other trace elements. The elements Neodymium, Dysprosium, Praseodymium are part of the group known as Rare Earths and are close to each other on the periodic table:

    When mining for rare earths, the ore dug out of the ground contains many of the rare earth elements in various concentrations. A good mine is generally one where 5% of the ore contains rare earths. That fraction of rare earth is then subdivided, with some elements being more prevalent than others. Usually, Neodymium and other elements that are useful for magnets are only a tiny fraction of that original 5%. But Cerium is, by far, the most prevalent element.

    While Cerium is a rare earth element, there haven’t been many applications that utilize it. Until now, the only noteworthy usage has been glass polishing and even that uses only a small fraction of the available Cerium.

    So Why Now?

    standard vs cerium neodymium magnetGiven its lack of usage, there’s now a surplus of Cerium. Magnet manufacturers began experimenting with this surplus and found that substituting Cerium for some of the Neodymium can produce an effective and lower-cost magnet. Although magnets containing Cerium are a bit weaker than traditional Neodymium magnets, they can be used in less demanding applications for a meaningful cost savings.

    Aside from the performance hit, magnets containing Cerium look and behave exactly like their non-Cerium counterparts. They can be easily plated with nickel or zinc and will weigh the same.

    Pros and Cons

    As of January 2023, Neodymium was selling for $73 per kilogram. At the same time, Cerium was selling for $2.2 per kilogram. Since Cerium is substituting for some, but not all, of the Neodymium magnet and factoring for processing costs, the result is a 5% to 10% price reduction.

    However, since Cerium isn’t as effective as Neodymium at producing magnetism, magnets containing Cerium are generally only available in the lower grades, from Neo30 to Neo42.

    At moment, the default is to offer non-Cerium magnets. However, if an application warrants it, we may suggest it as an option. Want to learn more about Cerium and its cost-saving potential? Contact our engineering team today!

     

  6. All of Your Permanent Magnet Questions Answered in New Permanent Magnet Reference Guide

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    Adams Magnetic Products is proud to announce the release of A3’s long-awaited Permanent Magnet Guide and Reference, spearheaded by our own Senior Applications Engineer, Mike Devine.

    The 111-page book includes easily understandable information about permanent magnetic products, their specifications, and applications, as well as helpful info about inspection, specification, and use, including the benefits and limitations of each material. A practical resource for anyone using or producing permanent magnetic materials, the book features a standard vocabulary, terminology, and symbols to help readers become more fluent in their understanding and usage of magnetic materials, assemblies, and systems.

    A must-have for anyone working in the magnet industry, the Permanent Magnet Guide and Reference is especially useful for engineers new to the field, businesses incorporating magnets into their product lines, and quality assurance operators. The guide also includes numerous references for additional research and discovery into specific areas of interest.

    Updating the guide, which was originally released in 1987, was a priority for Devine, who has chaired A3’s Permanent Magnet Division since January of this year. The A3 Permanent Magnet Division aims to increase the understanding, promotion, and effective use of magnetic materials, assemblies, and systems for the benefit of the Permanent Magnet Division members and all users of permanent magnet products. The Permanent Magnet Guide and Reference is a supplemental guide to A3’s Standard Specification for Permanent Magnet Materials and serves as a bridge between unit property data and a permanent magnet component having a specific size and geometry in order to establish a magnetic field in a given magnetic circuit environment.

    Order your copy of The Permanent Magnetic Guide and Reference here.

  7. Grab Your Glasses – This One’s 3D!

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    Did you know that Adams Magnetic Products utilizes 3D printing to improve our quality control,  R&D, and magnet production processes? Our 3D printers save our customers time and money by enabling us to create custom magnets and supporting parts on-demand, including rapid prototypes, proof of concept mockups, and customer samples.

    Having complete control of this additive process in house, we can make adjustments on the fly without waiting for expensive iterations to be built, shipped, and tested. This capability gives Adams a unique ability to create completely customized magnet solutions quickly and cost-effectively. And, with the ability to print in a wide range of materials, including GF/CF reinforced nylon, TPU rubber, ABS, and polycarbonate we can select just the right material, optimized for your industry and application.

     

    In addition to saving our customers time and money, and enabling our team to offer creative solutions quickly, our 3D printer has also improved the quality of our product range as a whole. 3D printed magnetizing, inspection, and assembly fixtures allow for a higher degree of repeatability, and consistency, along with overall more efficient and safe production processes.  Sometimes we even share these tools with customers so we can correlate data with identical fixtures.  The possibilities are endless!

    3D printed lab fixtures

     

     

     

     

     

     

     

    Give us a call today and let our team of experts and engineers help resolve your next magnet challenge!

  8. Leading the Industry in Customer Satisfaction

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    Adams Magnetic Products leads the magnetic products industry in customer satisfaction.

    NPS scoreHow do we know? Like many organizations, we use a customer survey tool called net promoter score, or NPS, to understand our customers’ perceptions. We ask our customers to answer a simple question on a bi-annual basis: “How likely is it that you would recommend Adams Magnetic Products to a friend or colleague?” responding with a rating between 1 and 10. Our NPS score is then calculated by subtracting the percent of respondents who ranked us between 0- 5 (called detractors) from the percent who ranked us 9 or 10 (called promoters). The resulting score can range from -100 to +100

    While a score of +100 is a nearly impossible achievement for any organization, Adams’ quarterly NPS scores are consistently above 90, a ranking considered “world-class” by NPS. You might call us the Nordstrom of the magnetic industry, except that our scores are even higher than theirs.

    We also provide an opportunity for customers to add comments. Recent NPS customer comments include:

    “Great service!”

    “I have dozens of vendors, and Adams is the top one for making purchasing and replenishment easy.”

    “Very satisfied with product and service.”

    “Customer service is excellent.”

    Why are our customers so happy? Because we have the right products available at the right times, eliminating frustrating supply chain interruptions. With more than 1 million magnets in stock, including the original round base magnet developed by Adams, we have the most extensive on-demand inventory in the country. Our strategically located redundant domestic facilities, consignment inventory options, and integrated systems (including ERP and ISO) exist to ensure our customers’ business continuity, something they value considerably given today’s supply chain difficulties, natural disasters, and other situations impacting availability.

    Our happy customers represent a vast array of industries. In fact, Adams serves the largest range of industries and applications of our competitors. We also serve more Fortune 500 companies than any of our competitors. This is because we have more combined magnet knowledge and experience than our competitors. Our unparalleled prototyping capabilities and vastly experienced product application team mean we’re better – and faster – at understanding our customers’ requirements and translating them into high-quality, manufacturable magnets and assembles. As a result, we’re proud to offer the fastest new product response times in the industry.

    Don’t believe us? Just ask some of the more than 100,000 satisfied customers who have purchased more than 1 billion magnets from Adams over the last 70 years.

  9. Measuring Remanence and Coercivity with a Hysteresisgraph

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    When you come right down to it, permanent magnets have two major features:

    1. They produce magnetic fields
    2. They resist demagnetization

    As with any technology that’s been around for a while, the industry has specific terms to describe these features: Remanence and Coercivity.

     

     

     

     

     

     

     

     

    Remanence tells the user how much output a magnet material grade can produce, depending on volume, shape, temperature, and other factors. A steel nail can produce a lot of magnetic output, but it needs an energized coil around it to produce that field. Once the electricity to the coil is turned off, it stops producing a magnetic field. A permanent magnet can also produce a lot of magnetic output, but it does it without an energized coil.

    • Remanence for steel in a nail: Up to 20,000 Gauss (2 Tesla)
    • Remanence for a Rare Earth magnet: Up to 14,500 Gauss (1.45 Tesla)

    Coercivity tells the user how hard it can be to demagnetize or weaken a magnet material, also depending on volume, shape, temperature, and other factors. The higher the coercivity, the harder it is to demagnetize. The steel nail from the previous example is easy to demagnetize, so easy it is effectively demagnetized when the electricity to the coil is turned off. By contrast, a Rare Earth Permanent magnet is extremely difficult to demagnetize.

    • Coercivity for steel in a nail: Up to 1 Oersted (80 kiloAmpere/meter)
    • Coercivity for a Rare Earth magnet: Up to 40,000 Oersteds (3,184 kiloAmpere/meters)

    The vast majority of magnet test equipment focuses on measuring the first feature, the magnetic output of a permanent magnet or permanent magnet assembly. However, only one instrument can measure both the Remanence and the Coercivity of a material: The Hysteresisgraph.

    Adams lab hysteresisgraphWith a suitably sized test specimen, generally the size of a sugar cube, the hysteresisgraph magnetizes and demagnetizes the material, accurately measuring the Remanence and Coercivity. This is crucial if your magnetic device is going to operate in an environment with demagnetizing fields. One needs to be certain the material will have enough demagnetization resistance for the job.

    measuring coercivity and remanence with hystergraf

    Adams has hysteresisgraph equipment at each of our manufacturing facilities and is constantly used to verify material properties.

    Any questions?  If so, please contact us.  We’re here to help!

  10. What is the MAGNETIC MOMENT?

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    The magnetic moment is a property that we use to verify the quality of our magnets. It is a way to measure the strength of a magnet and is widely used throughout the industry. Moreover, it is an easy, quick, and repeatable measurement.

    The magnet grade and magnet volume define the magnetic moment. Testing for it confirms:

    1. the correct magnet grade was chosen,
    2. the magnet has the correct dimensions & orientation, and
    3. the magnet was fully and properly magnetized.

    The magnetic moment is a measurement of the overall magnetic output of a magnet. Many illustrations of magnets show ‘lines of flux’ going from one magnetic pole to the other:

    Magnetic lines of flux from a cylinder-shaped magnet

    So, the magnetic moment is the summation of all those lines. Assuming the magnet is fully and properly magnetized, the two main factors determining the magnetic moment are the Type/Grade of magnet material and the Volume of a magnet.

    • The stronger the magnet grade, the larger the magnetic moment
    • The larger the magnet volume, the larger the magnetic moment

    As a rough approximation, the four major types of permanent magnet material can be ranked lowest to strongest:

    1. Hard ferrite/Ceramic
    2. Alnico
    3. Samarium Cobalt
    4. Neodymium Iron Boron

    For the same size magnet, here is an illustration depicting the relative magnetic lines of flux:

    In conclusion, here are some examples:

    • The Earth’s magnetic moment is 8 x 10 22 Ampere-meter2
    • A bowling ball made of Neodymium Iron Boron (strongest grade) would have a magnetic moment of 5937 Ampere-meter2
    • A Neodymium Iron Boron (strongest grade) disc the same size as a US Penny would have a magnetic moment of 0.4824 Ampere-meter 2
    • A Neodymium Iron Boron disc in a typical mobile phone has a magnetic moment of 0.007909 Ampere-meter2

     

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