Enhanced Room-Temperature Ferromagnetism in Superconducting Pr_2-<i>_x</i>Ce<i>_x</i>CuO₄ Nanoparticles

Abstract

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.

Synchrotron X-Ray Absorption Spectroscopy (XAS) Studies on Structural and Magnetic Properties of T’-Pr_2-xCe_xCuO₄ Nanocrystals

“…M. A. Baqiya, et al [15] reported that there is a magnetic transition from weak ferromagnetic to paramagnetic behavior after the reduction annealing in argon. An enhancement of ferromagnetism was also observed at room temperature in the optimally reduced PCCO nanoparticles [16]. This confirms the effect of oxygen vacancy on the magnetic properties of the PCCO nanocrystals.…”

A Structural Investigation of T’-Pr2-xCexCuO4 nanocrystals with x = 0.13

“…The search of the high-T c superconductors (HTS) and their behavior opens a new hidden promising property. The socalled apical oxygen is known to be responsible for presenting magnetic behavior, namely, weak ferromagnetic features at room temperature [1]. By means the tetravalent ion doping, a crystalline defect may appear at the apical site and/or at the in-plane oxygen site exhibiting a dominant paramagnetic behavior with a minor weak ferromagnetic feature [2].…”

“…Currently, it is found that the defect recovery on the T'-type structure can be strongly reduce the vacancy at the surface of the nanoparticles [6] in contrast to the full annealing oxygen reduction at vacuum atmosphere [1,2]. This may be related to the number of vacancies recovered and/or created in the nanoparticles.…”