Protected Vacuum Annealing Effect on Single Crystals of Pr 1- x LaCe x CuO 4 in the Overdoped Regime

Triono

et al. 2020

KEM

We have succeeded in synthesizing electron-doped cuprates T’-Pr2-xCexCuO4 (PCCO) with x = 0 and 0.10 nanocrystals prepared by the chemically dissolved method. Reduction annealing of the PCCO samples at 700°C under a flowing argon gas atmosphere has been performed for the removal of excess oxygen in the apical sites. The XRD data showed that the reduction annealing process decreases c-axis length indicating successful removal of the excess oxygen. The bond distortion of PCCO including coordination number and bond distance between the absorber atoms with the nearest neighboring atoms (Cu-O) was investigated by extended x-ray absorption fine structure (EXAFS) using Cu K-edge. The implication of our results is discussed on the basis of tremendous influence of oxygen vacancies on the magnetism of the nanosized T’-cuprates at the normal state.

Section: Introductionmentioning

confidence: 99%

Synchrotron X-Ray Absorption Spectroscopy (XAS) Studies on Structural and Magnetic Properties of T’-Pr2-xCexCuO4 Nanocrystals

Triono

et al. 2020

KEM

“…The Ce-doping effect may contribute the crystalline defect on the T'-PCCO [16]. However, during the partial reduction, there is no vacancy created on the O(3) site compared to the normal annealing in the previous studies [7,17]. The O(3) oxygen seems to be difficult to remove.…”

Section: Resultsmentioning

confidence: 89%

Possible Defect Recovery in T’-Pr2-xCexCuO4 with x = 0.10 Nanoparticles Analyzed by Neutron Diffraction

Insani

et al. 2021

MSF

We report the possible existence of defect recovery and the magnetic behavior in the T’-Pr2-xCexCuO4 (T’-PCCO) with x = 0.10 nanoparticles through the partially reduction annealing process. The powders of T’-PCCO nanoparticles were synthesized by using the chemically dissolved method followed by partially reduction annealing at 700 °C for 5 h in argon atmosphere. The high-resolution neutron powder diffraction (HRPD) technique has been employed to study the nuclear structure, vacancy, and the magnetic properties of the T’-PCCO nanoparticles. It is found that there is an increase of oxygen occupancy at the in-plane oxygen, O(1), and the apical oxygen, O(3), which signifies the decrease of the number of the vacancy on their sites. Meanwhile, the out plane oxygen, O(2), seems to be unchanged in the partially reduced samples. The Fourier difference profile shows an enhancement of the neutron scattering density at all the critical sites of O(1), O(3), and the Cu site. This may lead to the idea of the defect recovery affecting the whole magnetic moments which is responsible for the absence of weak ferromagnetism in the T’-PCCO nanoparticles.

“…This is important to achieve superconductivity as reported in Refs. [18,19]. However, it should be noted that not only oxygen at this site can be removed, but also oxygen at the other sites in the T'-structure, namely in O( 1 In this research, a low annealing temperature with a short holding time was carried out to maintain the nano-sized particles and avoid the phase decomposition as much as possible.…”

Section: Resultsmentioning

confidence: 97%

“…Therefore, the oxygen reduction in the atmosphere with a low partial pressure or in vacuum is very crucial to achieve its superconductivity [17]. Thus, it has been suggested that superconductivity will not occur only by Ce-doping, but an annealing process in vacuum must be carried out to reduce the oxygen content [18][19][20]. In order to obtain superconducting samples and to observe the enhancement of magnetization, in this work, the PCCO nanoparticles were reduced in vacuum with increasing annealing temperature.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Room-Temperature Ferromagnetism in Superconducting Pr2-xCexCuO4 Nanoparticles

Baqiya

et al. 2019

MSF

Recently, the so-called room-temperature ferromagnetism in any nanoparticles has been studied intensively. It is well known that the properties of ferromagnetism and superconductivity are contradictory in a superconducting high-Tc cuprate. The existence of ferromagnetism in the nanoparticles has been suggested to occur on the surface. This magnetism has been expected to come from defects inducing magnetic moments on oxygen vacancies at the surface of the nanoparticles. This work is to observe magnetism in nanosized superconducting Pr2-xCexCuO4 (PCCO) with x = 0.15 by means of a superconducting quantum interference device (SQUID). The magnetization curves of the reduced PCCO nanoparticles with the superconducting transition temperature, Tc, of ~25 K have revealed that there is weak ferromagnetism observed at room temperature. The magnitude of magnetization could be enhanced by oxygen reduction annealing in vacuum with increasing annealing temperature. A non-linear magnetization occurring in the reduced PCCO nanoparticles through the vacuum annealing process is probably due to a strong oxygen reduction producing more oxygen vacancies in the T'-structure.