These high values render hardened tungsten-steel particularly suitable for the manufacture of permanent magnets.
In its improved form this meter consists of a single horseshoe permanent magnet formed of tungsten-steel having a strong and constant field.
For soft iron, tungsten-steel and nickel little difference appeared to result from lowering the temperature down to - 186° C. (the temperature of liquid air); at sufficiently high temperatures, 600 to 1000° or more, it was remarked that the changes of length in iron, steel and cobalt tended in every case to become proportional to the magnetic force, the curves being nearly straight lines entirely above the axis.
They found that the permeability of Swedish iron, tungsten-steel and nickel, when the metals were cooled to - 186°, was diminished in weak fields but increased in strong ones, the field in which the effect of cooling changed its sign being 115 for iron and steel and 580 for nickel.
The hysteresis-loss in Swedish iron was decreased for inductions below about 9000 and increased for higher inductions; in tungsten-steel, nickel and cobalt the hysteresis-loss was always increased by cooling.