Peculiarities of magnetic properties of the garnet Y2.25Gd0.75Fe5O12 irradiated by fast neutrons

Polycrystalline yttrium-gadolinium iron garnet samples irradiated by different fluences of fast neutrons ((0 to 2.0) x 1024 m-2) were investigated by magnetic and X-ray methods. Irradiation was found to increase the temperature of sublattice magnetization compensation from 5 to 47 K. The increase was attributed to the different behaviour of gadolinium and iron sublattices under irradiation. In the irradiated samples negative magnetization states were found to arise in the vicinity of the compensation point. The phase H-T diagram of such states was plotted based on the measurements performed. The cause of a negative magnetization occurrence was shown to be the intersection of a spin reorientation with respect to temperature in the compensation point and a freezing of magnetic moments of ferrimagnetic clusters in a spin-glass matrix. (orig.)