According to the Encyclopaedia Britannica, iron, cobalt and nickel all share the property of ferromagnetism. This means that of the elements on the periodic table, these three are the only transition metals that have magnetic properties.
Being ferromagnetic means that iron, cobalt and nickel can be magnetized easily and formed into permanent magnets. It is also associated with the element gadolinium, which is part of the lanthanoid series.
Iron, cobalt and nickel are in consecutive order on the periodic table, designated with atomic numbers 26, 27 and 28 respectively. They are immediately followed by copper (29) and zinc (30), neither of which are ferromagnetic.