Editing Temperature coefficient (section)

==Reversible temperature coefficient==
[[Remanence|Residual magnetic flux density]] or '''B'''{{sub|r}} changes with temperature and it is one of the important characteristics of magnet performance. Some applications, such as inertial [[gyroscope]]s and [[traveling-wave tube]]s (TWTs), need to have constant field over a wide temperature range. The '''reversible temperature coefficient''' (RTC) of '''B'''{{sub|r}} is defined as:
:<math>\text{RTC} = \frac{|\Delta\mathbf{B}_r|}{|\mathbf{B}_r|\Delta T} \times 100\%</math>

To address these requirements, temperature compensated magnets were developed in the late 1970s.<ref>{{cite web |url=http://www.electronenergy.com/about-us/about-us.htm |title=About Us |publisher=Electron Energy Corporation |url-status=dead |archive-url=https://web.archive.org/web/20091029044111/http://www.electronenergy.com/about-us/about-us.htm |archive-date=2009-10-29 }}</ref>  For conventional [[Samarium–cobalt magnet|SmCo magnets]], '''B'''{{sub|r}} decreases as temperature increases.  Conversely, for GdCo magnets, '''B'''{{sub|r}} increases as temperature increases within certain temperature ranges. By combining [[samarium]] and [[gadolinium]] in the alloy, the temperature coefficient can be reduced to nearly zero.