Low temperature magnetic order and the insulator to metal transition in the Y1-xCaxBa2[(Cu0.992Fe0.008)-Fe-57](3)O-6.1 system studied by Mossbauer spectroscopy

Deoxygenated Y1-xCaxBa2[(Cu0.992Fe0.008)-Fe-57](3)O-6.1 compounds with calc ium content of x=0.05, 0.08, 0.12, 0.16, 0.2, 0.26 wee prepared by the stan dard ceramic method. The system exhibit insulator to metal transition. The onset of supercondudivity is detected in the sample with x=0.26. The influe nce of doped holes on low temperature antiferromagnetic order has been inve stigated. Low temperature Mossbauer spectra consist of two sextets with rel ative ratio changing with hole concentration. The sextets are broadened, th eir shape and temperature dependence indicate the existence of magnetic ord er fluctuations with the relaxation time slightly highs than the observatio n time of the method similar to 10(-7) s.