…that’s what this blog brings you.

One material works nicely: the element gadolinium (Gd). It’s a
silvery-white metal that’s strongly attracted by a magnet, has a
magnetic disordering temperature of 20C, and a giant magnetocaloric
effect of several degrees. A waste product from permanent magnet
manufacture, gadolinium costs around £100 per kg; a magnetic fridge
would use 0.15kg. Sandeman’s current research, however, is looking at
other possibilities.

"The quest is to get away from these
expensive rare earth materials and look for magnetic materials which
have a phase transition at room temperature," says Sandeman, whose
research job at Cambridge University is funded by the Royal Society. He
also works with Professor Derek Fray, a leading expert in materials
chemistry. "What I’m actually working with is an alloy of two magnetic
materials, cobalt and manganese," says Sandeman.

This blog, April 2005:

Another is the work on gadolinium based magnetic refrigeration, still in its infancy, but we know it works.

BTW, anyone who thinks that gadolinium is £100 per kg in quantity needs their head examined. Rare earth metals should be just above twice the cost of the oxide they are made from.