Observation of weak magnetic feature in the partially reduced T’-Pr2-xCexCuO4 powders by using neutron diffraction technique

Abstract

The magnetic feature of the superconductor material is a challenging issue in the work of searching the new High-Tc Superconductor (HTSc). The role of magnetic feature including its magnetic structure may be the key to understand the true mechanism of the superconducting materials with a higher critical temperature Tc. The purpose of this research is to observe the weak magnetic feature in the reduced T’-Pr2-xCexCuO4 (T’-PCCO) with x = 0, and 0.15 powders using neutron powder diffraction (ND) technique. The reduced powders were obtained by the chemically dissolved method and then continued by a short reduction annealing process at 700°C for 5 h. The profile refinements of both ND patterns show an indexed peak of PCCO phase with I4/mmm space group. The careful Rietveld analysis shows a coupled magnetic contribution at some of the nuclear Bragg position indicating a weak magnetic feature with propagation vector k (0.5 0.5 0) on both reduced samples. Interestingly, the magnetic unit cells are found to be not a simple periodic order of the chemical unit cell and the corresponding spins could be arranged even more than just antiferromagnetic ordering. The Ce-dependence of the volumetric unit cell is confirmed and consistent with the bond valance sum calculation. The scattering density via Fourier transform calculation shows the remnant magnetic interaction is relatively small compared to its combined nuclear and magnetic phases. This signifies the existence of a weak magnetic feature in the T’-structure. Moreover, the magnetic refinement confirms the decrease of collective magnetic moments of T’-PCCO with x = 0 and 0.15 in.the reduced system showing an antiferromagnetic spin arrangement due to recovery of apical oxygen.