Introduction of columnar defects in colossal magnetoresistive manganites by heavy ions irradiation

The effects of swift heavy Pb (6 GeV) ions irradiation have been studied in the colossal magnetoresistive (CMR) Pr-0.7 Sr0.3MnO3 compound. High-resolu tion electron microscopy (HREM) has shown that the induced defects are near ly continuous amorphous columns. The resistivity is slightly increased by t he irradiation, due to the presence of the defects. Furthermore, the coupli ng between the columnar defects and the strong Jahn-Teller distortion exist ing in the related compound Pr0.7Sr0.1Ca0.2MnO3 also decreases the Curie te mperature. The magnetic hysteresis in the ferromagnetic state is strongly i ncreased in the irradiated samples, reflecting the hindrance of the magneti c domain walls (DWs) by the induced defects. The strong pinning regime of t he DW by the defects is shown to be relevant to: our experiment. A model ba sed on this strong pinning effect is used to qualitatively explain the coer cive field dependence on the density of defects. (C) 2001 Elsevier Science B.V. All rights reserved.