Nickel Irons & Soft Magnetics

Low-loss core materials

Arnold Precision PTM provides thin-rolled nickel-iron alloys and soft magnetic materials used for efficient energy storage and transfer. Nickel-iron alloys are characterized by relatively high permeability and low core losses. Their overall high saturation flux density means high performance energy storage and transfer over low to middle frequencies.

Our precision rolled Nickel-iron materials are used in devices such as transformer cores, toroids, sensors, motor laminations, watch springs, flapper valves, and power springs, and various shielding applications.



Materials and composition (% weight)


Ni Mo Mn Si Fe C V Nb Co Cr Al Ti
Moly Permalloy 80.0 4.8 0.5 0.35 Bal. --- --- --- --- --- --- ---
Supermendur --- --- --- --- 49.0 --- 2.0 --- 49.0 --- --- ---
Permendur --- --- --- --- 49.0 --- 2.0 --- 49.0 --- --- ---
Alloy 43 42.5 --- 0.5 0.5 Bal. 0.03 -- -- -- 5.25 0.5 2.5
Alloy 48 48.0 --- 0.8 0.3 Bal. (1) 0.05 -- -- -- 0.25 0.1 ---
Alloy 49 48.0 --- 0.5 0.35 51.0 0.02 --- --- --- --- --- ---
MuMETAL® 79.0 - 80.6 3.8 - 5.0 0.95 0.42 Bal. (2) 0.03 --- --- --- --- --- ---

(1) P 0.025 max; S 0.025 max
(2) P 0.02max; S 0.008 max
Phosphorus and Sulfur contents are noted on these grades because they are very detrimental to the material if they exceed the maximums.

Materials characteristics

Moly Permalloy has high magnetic permeability suitable for electromagnetic shielding.

Supermendur and Permendur have high flux density, suitable for transformers or chokes.

Alloy 48 (Nilo 48) and Alloy 49 are nickel-iron controlled-expansion alloys containing 48% nickel. Alloy 48 (Nilo 48) coefficient of thermal expansion matches that of soft lead and soda lime glasses; therefore Alloy 48's main use is for glass to metal seals in soft lead or soda lime type glasses. Alloy 48 is also used for thermostats in industrial applications up to 840 F (450 C).

Alloy 49 has high permeability for use in laminated cores for instrument transformers, magnetic shielding, and cores for electronic and communications devices for which extremely high permeability at low magnetizing forces greatly increases the efficiency and effectiveness of the equipment. Because of its high permeability, it has also been used in solenoid cores in light-sensitive relays that must operate and respond to weak currents that induce low magnetizing forces.

MuMETAL® has extremely high initial permeability. It is only moderately resistant to moisture and atmospheric corrosion. Used in transformer cores, Mu metal is widely used for shielding electrical components from magnetic fields.

Available in a range of thicknesses and widths

Thickness Maximum Width
0.01" - 0.0004" (0.254 - 0.0102mm) 12.5" (317.5mm) as rolled edge
12.0" (304.8mm) with a slit edge
0.00039" - 0.00008" (0.0099 - 0.0020mm) 4.25" (107.95mm) as rolled edge
4.0" (101.6mm) with a slit edge


Magnetic properties

  Permeability at B = 20 Gauss Maximum Permeability Saturation Flux Density
Moly Permalloy 20,000 100,000 8,700
MuMETAL® 20,000 100,000 6,500
Supermendur 800 4,500 24,000
Permendur 800 5,000 24,500
Alloy 48 4,000 50,000 16,000
Alloy 49 4,000 50,000 16,000


MuMETAL® is a registered trademark of Magnetic Shield Corporation