Kainchild - that is exactly what Peteeo offered you - 60Co and isotopes of the others are radioactive and can be made into magnets. Can just any old metal be made into a magnet? No. Very few actually can be.
From Day& Selbin. Theoretical Inorganic Chemistry. 2nd Ed' "Magnetic Phenomena in chemical substances may arise from both electrons and nucleons. However, the magnetic effects due to electrons are of the order 1000 times greater than those due to nucleons and nuclei. Therefore,except for the chemical information obtainable from NMR.....arising from elcetons alone will be of interest to the chemist. "
I would interpret this as magnets made from radioactive materials would be hard to tell from non radioactive....well maybe...warm, glowing.... (all depends on how much you've alloyed in)
Peteeo is absolutely correct. A magnetic made of radioactive isotopes of an element would be capable of the same magnetic fields as a magnet made of non-radioactive isotopes of the same element.
One thing we've not discussed is the radioactive decay process itself. The elements used will loose both their nuclear and electronic structure.. and therefore their magnetism
The would loose their magnetism at the same rate that they decay.
He is saying that radioctive magnets would lose their radiation faster than non-radioactive ones. How much faster would depend on the isotope. Isotopes that decay quickly wouldn't hold their magnetism long. If the decay was slow enough, the loss in magnetism wouldn't be noticible compared to a non-radioactive isotope.
btw, I realized I have been throwing the term isotope around but never defined it. In case you don't know what it means, I'll explain. Atoms are made up of protons, neutrons, and electrons. The number of protons determines what element the atom is. Some combinations of protons and neutrons are fairly stable. Others are unstable. The unstable ones will decay and release radiation as they do so. An Isotope is simply a specific combination of protons and neutrons.