Early Studies of Superconductive Materials and Superconducting Magnet in China(1962～1966)

On the basis of the published literature and the interviews with some participants,this paper introduces the early history of the studies of superconductive materials and superconducting magnet during 1962～ 1966 in China,narrates the achievements of other relevant experimental and theoretical studies of superconductivity in that period briefly,and tries to give the authors' comments on that history.

Superconducting Magnetic Flux Transformer at 77K

Superconducting Quantum Interference Device (SQUID) magnetometer is a kind of magnetic flux sensor with high sensitivity, and therefore can be used in geological prospect and biomagnetic field etc.. But the SQUID magnetometer used before has to be used at the temperature of 4.2K provided by liquid helium and thus its application is limited. Since the discovery of high Tc oxide superconductors, scientists have been trying hard to put the SQUID magnetometer into use at 77K. Recently, a new kind of high Tc superconducting magnetic flux transformer winded with one piece of BiPbSrCaCuO superconducting wire is produced. The magnetic flux transformer can be designed to be insensitive to both uniform fields and fields with a constant gradient. In this letter, the fabrication and the properties of the high Tc superconducting magnetic flux transformer is described.

Observation of lateral long range order in superconducting FeTe thin films

We find that the superconductivity in the thin films of the formerly believed non-superconducting parent compound FeTe is accompanied by an emergence of second order with a correlation length of 742 nm and 258 nm at 10 K and 300 K, respectively. The structural phase transition found in iron pnictide superconductors, in non-superconducting FeTe bulk samples, and in FeSe superconducting thin films is not observed in the superconducting FeTe thin films. The interplay between superconductivity and long range order may suggest the crucial role of competition between electronic localization and itinerancy which leads to strong quantum fluctuations in the FeTe system.

INFLUENCE OF GEOMETRICAL CONFIGURATION OFSUPERCONDUCTING MATERIAL ON GROWTH OF Nb_3 Sn

Boundary conditions constructed by two typical geometrical configurations related to the manufacturing methods of bronze process and tin-rich Nb tube method have been considered in a diffusion model in which the diffusion of Sn in CuSn matrix plays a major role is as- sumed.The dependence of thickness of Nb_3Sn layer on reaction time has been derived.It is shown that the growth rate of Nb_3Sn relates to the configuration of the superconductor,the geometrical parameters of Nb filaments and CuSn matrix.The theory is qualitatively con- sistent with the experimental results.

High T_cHoBa_2Cu_3O_（7－δ） Thin Films Deposited on （100） Y_2O_3 Stabilized ZrO_2 Substrates by Sputte

Thin films of superconductors HoBa_2Cu_3O_(7-δ)(HBCO) were prepared by DC-sputtering technique. The epi-taxial growth was controlled by the ratio of the oxygen pressure and Ar pressure (O_2/Ar) , the subetrate temperature T_s and the distance of the target to subetrate. Thin films deposited under the optimum conditions (Po_2/P_(Ar)= 1:2 ; T_s=730℃) show a critical temlierature clase to 87K and a transition width less than 1K. X-raydiffraction analysis shows that the films are highiy c-axis oriented. Auger electron spectroscopy depth profilingdemonstrates Ho diffusion into the Zr(Y)O_2 subetrate owing to the Ho subetitution for Y.

Ferromagnetic half levitation of LK-99-like synthetic samples

We successfully synthesized polycrystalline LK-99-like ceramic samples with a solid-state-sintering method.Powder X-ray diffraction shows that the main contents are Pb_(10-x)Cu_(x)(PO_(4))_(6)O and Cu_(2)S,consistent with recent reports (arXiv:2307.12037;arXiv:2308.01192).In some small flaky fragments,we successfully observed“half levitation”atop a Nd_(2)Fe_(14)B magnet.Using magnetization measurements on such small pieces,as well as on a large piece which does not exhibit the half levitation,we show that the samples ubiquitously contain weak yet definitive soft ferromagnetic components.We argue that,together with the pronounced shape anisotropy of the small fragments,the soft ferromagnetism is sufficient to explain the observed half levitation in strong vertical magnetic fields.Our measurements do not indicate the presence of the Meissner effect,nor zero resistance,in our samples,leading us to believe that our samples do not exhibit superconductivity.The precise chemical composition and the physics behind the ferromagnetic component remain outstanding questions to be addressed in future research.