mu - phonetic spelling of the Greek letter μ, which is typically used as a symbol of magnetic permeability.¹⁾

The notation mu is used especially when only basic alphanumeric input method is available, without the possibility of using special characters, such as those from Greek alphabet.

Wound cores made from Mumetal tape

^{S. Zurek, E-Magnetica.pl, CC-BY-4.0}

The trademarked name Mumetal²⁾ was created to denote that this special Ni-Fe alloy exhibits very high permeability.

Similar, the trademarked name Kool-Mu³⁾ (magnetic material made of sintered powder) is related to its high permeability (“mu”) and low magnetic loss (“kool”) exhibiting lower heat dissipation, hence cooler operating temperature for cores with the same size (and the same thermal resistance).

• μ
• Magnetic permeability
• Mumetal
• Kool-Mu