MAGNETIC ORDERED STATES IN THE OXYGEN-DEFICIENT YBA2(CU1-XFEX)3OY-LESS-THAN-6.5 SYSTEM

The magnetically ordered states in the oxygen-deficient YBa2(CU1-xFex)3Oy<6.5 system (0.01 less-than-or-equal-to x less-than-or-equal-to 0.30) have been studied by Mossbauer spectroscopy. Magnetic ordering of Fe atoms is found at Cu(1) sites as well as at Cu(2) sites. At small iron concentrations x less-than-or-equal-to 0.05 the Cu(1) and Cu(2) sublattices are not coupled magnetically and two magnetic phase transitions are observed: the low-temperature transition for the Cu(1) sublattice at T(m1) almost-equal-to 20 K and the high-temperature transition for the Cu(2) sublattice at T(m2) almost-equal-to 400 K. With increasing iron concentration at x greater-than-or-equal-to 0.10 a strong coupling between the Cu(1) and Cu(2) sublattices appears and the whole matrix is ordered antiferromagnetically with a single magnetic ordering point T(m2) almost-equal-to 460 K. The phase diagrams showing the regions of existence of different magnetic phases versus iron concentration are plotted for the oxygen-saturated and oxygen-reduced YBa2(CU1-xFex)3Oy systems.