metamagnets

English: The magnetic field of a bar magnet revealed by iron filings on paper. A sheet of paper is laid on top of a bar magnet and iron filings are sprinkled on it. The needle shaped filings align with their long axis parallel to the magnetic field. They clump together in long strings, showing the direction of the magnetic field lines at each point. (Photo credit: Wikipedia)
Newly Identified ‘Universal’ Property of Metamagnets May Lead to Magnetic Refrigeration