There are new appliances in my neighbors kitchen with stainless front.
Very classy. However they no longer have refrigerator art gallery as
magnets do not stick. Is there no soft iron in stainless fronts of these
new appliances? I am confused and hope you can guide me.
Stainless steel is an alloy, primarily iron with significant amounts of nickel &
chromium. (Other elements in small amounts are often added for various subtle
reasons.) Stainless steel IS ferromagnetic, it just has a Curie temperature
below room temperature :-)
(Ferro)magnetism is due to relatively weak interatomic forces on electrons.
There is always a competition between magnetic order and thermal disorder (much
like the competetion between superconducting order and thermal disorder). There
is a distinct, reversable phase transition between ferromagnetism/paramagnetism
at a temperature called the "Curie temperature" - above this temperature the
material is not ferromagnetic and will not be attracted to a magnet, below this
temperature, the material will be attracted to the magnet. The temperature
varies from material to material: 1043K for Fe, 627K for Ni, 292 K for Dy, etc.
By alloying "impurities" into the iron, the curie temprature drops (the
interactions between the electrons are weakened so thermal energy can more
easily disrupt the long range electron order). For typical "stainless steel"
the curie poit is below room temperature. Maybe if the insulation were poor
enough, the magnets would stick ;-)