Conventional semiconductor-based electronic devices can cause errors when they are exposed to cosmic rays. Magnetic memory has been proposed as an alternative because it consists of a metal structure free from radiation-induced errors in principle. In this study, we investigated the effects of proton and Cr ion irradiations on the magnetic and electric properties of a magnetic tunnel junction (MTJ). We observed that the magnetic hysteresis and magnetoresistance of MTJ were not affected by proton irradiation of an energy of 20 MeV and dose levels up to 1 x 10(18)/m(2), thus demonstrating good radiation hardness in response to the proton beam. On the other hand, when a MTJ was irradiated by a Cr ion beam of an energy of 20 keV and dose levels up to 1 x 10(18)/m(2), its magnetic properties or magnetoresistance deteriorated, depending on the layer structure of the MTJ. A simulation study shows that this degradation may stem from radiation-energy dependent displacement damage in the magnetic layers, which can be avoided by the introduction of a proper protective layer.