Manganese has magnetic moment so I think it's magnetic moment might affect the superconductivity of the sample.
If you dope Mn on Cu site then the superconducting transition temperature Tc will go down. In the early days of the research on high-Tc materials people have tried to substitute almost all possible elements of the periodic table and were disappointed to find that Tc goes down only. But if you substitute any magnetic material on the Gd site then Tc may in favorable cases remain the same or go down as well. In fact all other rare earth R^3+ ions on the Gd site will maintain Tc value around 92 K or so.
I am not sure whether you can succeed in putting Mn^2+ on Ba^2+ site? Have you done that and are you sure that Mn ions are on the Ba^2+ site entirely? In any case my guess is that Tc would decrease.
Thank you for the answer. I have been doing the substitution and at the same time trying to add Mn outside GdBCO. I would like to confirm that doing both will have the same effect on the sample. On the other hand, I am also looking on the possible pinning of flux that can possibly happen due to Mn.
What do you mean by adding Mn outside GdBCO? Physical mixture of GdBCO and Mn? Which Mn? \alpha, \beta, \gamma or \delta? You know there are several forms of Mn? Why do you think GdBCO and Gd(Ba1-xMnx)CO will be the same? With which respect? Tc? But I suppose the pinning of flux can happen due to Mn doping.
I meant sample preparation of pure GdBCO and Mn will be added as composite. I have been adding MnO on the sample. I believe that MnO is insoluble to the compound so at certain concentration limit, both doping and addition will produce the same results. Also the same as its effect on the Tc of the sample.
Look, the Mn solubility in (RE)123 compounds is rather low, close to 2.5 at.% @ the Cu sites. It seems that such a partial substitution does not affect Tc which is maintained close to 92 K. On the other hand, you may alter the sintering temperature of the material to 970 C. At this T, the sintering process is assisted by a liquid phase and all the samples have a quite different morphology and so on !
I suppose the first systematic study on this particular subject was made by our group and it has been published PRB 38, 4580 (1988). After that, few papers on the same subject , may be of interest: (i) Solid State Communications 68, 835 (1988); (ii) Physica C 159, 306 (1989).
By trying to make the Cu substitution by Mn one will certainly observe the occurrence of extra phases in the samples. One of these extra phases has been found to exhibit a large (and negative) magnetoresistance and has been the prototype of Mn-based CMR materials (manganites), discovered in the early 90's (see, for instance, PRL 71, 2331 (1993)). VON HELMOLT was the first author of pioneer studies in these manganites, motivated by his findings in the electronic properties of these materials. For these early findings, please take a look in Physics Letters A 165, 473 (1992), Solid State Communications 82, 693 (1992), and Solid State Communications 80, 865 (1991).
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