Charles Edouard Guillaume discovered Invar in the 1890s. He was awarded the Nobel Prize in Physics in 1920 for his work on the FeNi system and the discovery of Invar alloys. Iron-nickel alloy (Ni-Fe precision alloy) is a low-frequency soft magnetic material with high magnetic permeability and low coercivity in weak magnetic fields. Early iron-nickel alloys were used for telephone communications, and heat treatment processes and vacuum melting methods were used to improve alloy properties.