Articles

Magnetometry Measurements: Considerations for Magnetic and First-Order-Reversal-Curve Measurements

Brad C. Dodrill, Lake Shore Cryotronics, Inc.

Magnetometers are used to characterize magnetic material properties. Magnetometry techniques can be broadly classified into two categories: inductive and force-based. Common inductive methods include vibrating sample magnetometry (VSM), extraction magnetometry, AC susceptometry and superconducting quantum interference device (SQUID) magnetometry. The two most commonly used inductive techniques are VSM and SQUID magnetometry. Alternating gradient magnetometry (AGM) is the most often used force-based technique. The measurement most commonly performed to characterize a material’s magnetic properties is that of a major hysteresis loop. The hysteresis or M(H) loop is typically used to determine a material’s saturation magnetization Ms (the magnetization at maximum applied field), remanence Mr (the magnetization at zero applied field after applying a saturating field) and coercivity Hc (the field required to demagnetize the material). More complex magnetization curves covering states with field and magnetization values located inside the major hysteresis loop, such as first-order-reversal-curves (FORCs), can provide additional information that can be used to characterize magnetic interactions and coercivity distributions in magnetic materials[1].

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Permanent Magnet Mistakes, Part Seven

Stan Trout, Spontaneous Materials

We conclude this series with the seventh and final blog, describing the many types of mistakes made with permanent magnets. My intent is to help engineers in the future avoid mistakes made in the past, and not to embarrass anyone.

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Recent Developments and Trends in Nd-Fe-B Magnets

Jinfang Liu, President and COO, Electron Energy Corp.
Melania Jasinski, Manager of Process Engineering, Electron Energy Corp.

Nd-Fe-B magnets have a wide variety of applications in aerospace, medical, semiconductor, telecommunications, power generation, oil & gas exploration and automotive industries.  There have been many new developments in recent years including high energy Nd-Fe-B grades, heavy rare earth free high intrinsic coecivity Nd-Fe-B grades, radially oriented anisotropic rings, and improved manufacturing processes. The Nd-Fe-B market has also met a lot of challenges and opportunities in recent years, including volatile raw materials market, overcapacity problems in China, and patent issues. This article will cover some of the recent technical advances and new trends in Nd-Fe-B magnets. Continue reading

Microstructure and Mechanism of Coercivity Enhancement of Sintered Nd-Fe-B Magnet by Grain Boundary Diffusion

Yong Ding, Xiangke Lv, Min Zhang,
Xiaodong Zhu, Qingzhong Yang
Ningbo Yunsheng Co., Ltd.

Rare earth element (REE) based Nd-Fe-B magnets have been widely used because of their excellent magnetic properties. The applications of Nd-Fe-B rare earth permanent magnets include hybrid electric vehicles (HEVs), power generators for wind turbines, high performance industrial motors, hard disk drives (HDD) for computers, traveling wave tubes for satellite communications, headphones and speakers, washing machines, and other consumer electronic devices. Furthermore, as well known, Dy and Tb are used as an additive to Nd-Fe-B magnets to increase the coercivity (because they increase the magneto-crystalline anisotropy) of magnets. But the magnetic moment of Dy and Tb are coupled anti-parallel to that of Fe, which decrease the magnetization and maximum energy product of the magnet. Continue reading

Is There an Optimum Price-Performance Metric for Permanent Magnet Materials?

John Ormerod, Principal and Founder, JOC LLC

Attend any magnetics conference or seminar and I can guarantee a slide will appear in someone’s presentation showing something along the lines of the year of introduction of a permanent magnet material versus the corresponding (BH)max. Continue reading

Low Weight – High Torque Motors for Commercial Drones

Lowell Christensen,  Consultant • Lowell Christensen LLC

We have heard of the desire to make home deliveries using commercial drones. There are several logistic issues with drone deliveries. These issues will soon be overcome and commercial delivery drones will be a fast growing application. This will require changes in motor design to meet the requirement for high torque in a low weight motor. Continue reading

Extending the Limits of the Sm2Co17 System

By Steve Constantinides  | Arnold Magnetic Technologies

The 2010-2011 rare earth crisis appears over. Prices are low and adequate raw material is available. Many of the efforts initiated to find a better non-rare earth permanent magnet have ended in disappointment. Programs such as Fe-nitride, core-shell exchange coupled magnets and enhanced alnico are continuing but with limited success to-date and significant hurdles remaining. It is in this framework that revisiting one of the more significant magnet materials seems a reasonable proposition. What material, you ask? Well, the strongest permanent magnet material at and above 150°C, the one with excellent corrosion resistance and superior temperature stability – Sm2Co17. Continue reading