STUDY OF FE-57 DOPED (Y,CA)BA2CU4O8 BY MAGNETIC-SUSCEPTIBILITY AND MOSSBAUER MEASUREMENTS

Superconducting samples of (Y1-yCay)Ba-2(Cu1-xFex)(4)O-8 with y = 0, x = 0.25%, 1.25%, 3% and y = 0.05, x = 0.5%, 1.5%, 3% have been prepare d under L.P.O-2 and H.P.O-2. A.C. susceptibility data indicate the pre sence of weak links. Mossbauer spectra show a large occupancy of Cu(2) sites by iron. At low T, iron orders magnetically with a concentratio n dependent T-N, and even for x = 0.25%, suggesting long range indirec t Fe-Fe interactions. This is discussed in connection with present mod els.