Abstract
A high-density single-phase submicrometer ceramic Mn{sub 3}O{sub 4} with a grain size d {>=} 0.06 {mu}m has been obtained by using spherically converging shock waves. The action of shock waves reduces the unit cell volume and increases the Curie temperature T{sub C}. The shape of the temperature dependences of reciprocal susceptibility x{sup -1} of a polycrystal and the submicrometer ceramic at T > T{sub C} is hyperbolic, which is typical of ferrimagnets. It is shown that the susceptibility of the ceramic in the region of short-range order at 78 K {<=} T {<=} 300 K is larger than that of the polycrystal, while the field dependences of the magnetization are nonlinear. The bombardment by electrons with a small dose of {phi} = 0.8 x 10{sup 18} cm{sup -2} increases the susceptibility of the submicrometer ceramic as well as that of the polycrystal. When the fluence increases to {phi} = 5 x 10{sup 18} cm{sup -2}, the susceptibility decreases, which can be explained by radiation-induced disordering and a change in the 'local' exchange interactions.
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