Sudesh Das, Saikat Bernhard, Christian Varma, G.D. 2014-10-15 In this paper, the effects of addition of (i) graphene oxide (GO), (ii) a series of rare-earth (RE, RE = La, Sm, Eu, Gd, Tb and Ho) oxides (REO) and (iii) a mixture of GO and rare-earth oxides (GO + REO) on the superconducting properties of MgB₂, have been studied with the help of electrical transport and magnetic measurements. All the samples have been prepared following the standard solid-state reaction route. We have used an optimum value of 1 wt% REO and 3 wt% GO for addition on the basis of previous studies. X-ray diffraction studies confirm the formation of hexagonal crystal structure (space group P6/mmm) of MgB₂ with small amounts of REB<em>_x</em> (<em>x</em> = 4 and 6) and MgO impurity phases in all the synthesized samples. We observe that the critical current density, <em>J</em>_c and upper critical field <em>H</em>_c2(0) improve significantly in the REO-added and GO-added samples with no significant change in critical temperature, <em>T</em>_c. A substantial enhancement in <em>J</em>_c(<em>H</em>) and <em>H</em>_c2(0) is observed with the GO + REO addition in MgB₂. The different flux pinning mechanisms in all the samples are studied and it is found that the point pinning is the dominant mechanism in the GO-added samples and grain boundary pinning is the dominant one in the REO added samples. We have seen the combined effect of both types of flux pinning mechanisms in GO + REO added MgB₂. application/pdf https://folia.unifr.ch/global/documents/304032 https://folia.unifr.ch/documents/304032/files/ber_esp.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1016/j.physc.2014.07.008 info:eu-repo/semantics/openAccess License undefined Physica C: Superconductivity. - 2014, vol. 505, p. 32–38 superconductor Critical temperature Critical current density Flux pinning MgB₂ info:eu-repo/classification/udc/53 Enhanced superconducting properties of rare-earth oxides and graphene oxide added MgB₂ http://purl.org/coar/resource_type/c_6501