Swift heavy-ion irradiation effects on the super-conducting material La_1.85Sr_0.15CuO₄

The effects of columnar defects produced by swift heavy-ion irradiation on magnetic flux pinning were studied for the polycrystalline La_1.85Sr_0.15CuO₄. The bulk specimens were irradiated with 3.5GeV ¹³⁶Xe³¹⁺ ions from a single direction or multi-directions in order to investigate the effects of columnar defect configuration. The magnetization hysteresis was measured with a super-conducting quantum interference device (SQUID) magnetometer, and the critical current density J_c and irrevers-ibility line were observed. In the specimens irradiated from multi-directions, more enhancement of the critical current density and larger shifts of the irreversibility line to higher fields were observed than in the specimens irradiated from a single direction.