We reviewed our various results on rutheno-cuprate magneto-superconductors RuSr2GdCu2O8(Ru-1212) and RuSr2(Gd0.75Ce0.25)2Cu2O10(Ru-1222). It is observed, that it is difficult to control the oxygen content of Ru-1212, though the same is possible up to some

calculated from the SAED pattern is around 27.5 Å, being close to the value determined from the X-ray diffraction data i.e. 27.493(1) Å.

The SAED pattern taken for the same sample from the a-b plane is shown in Fig. 7. Interestingly the a-b plane observed here is also clean without any superstructure. Recent neutron powder diffraction (NPD) studies [18] on Ru-1222 revealed that even though the RuO6 tilt angle is seen, no evidence of supercell reflections arising from extended regions of RuO6 rotations could be observed, in contrast to the case of the Ru-1212 phase [8,33]. Our SAED results thus corroborate the NPD results [18] in terms of the absence of superstructural spot at the centre of the a-b rectangle. It should however be remembered that the as-synthesized Ru-1222 sample studied here is deficient in oxygen.

Fig. 6. SAED pattern for an as-synthesized Ru-1222 sample taken with incident beam // b.

Fig. 7. SAED pattern for an as-synthesized Ru-1222 sample taken with incident beam // c.