Spin Correlation in the Electron-Doped High-T_c Cuprate Thin Films of La_2-xCe_xCuO₄

In high-T_c cuprates, the intimate relation between the antiferromagnetic (AF) spin correlation and superconductivity (SC) has been suggested in the hole-doped cuprates. In the electron-doped cuprate Pr_1-xLaCe_xCuO₄, on the other hand, neutron-scattering experiments suggested the robust AF correlation in non-superconducting heavily overdoped (HOD) regime [1], whereas muon-spin-relaxation (μSR) measurements suggested the disappearance of the development of Cu-spin correlation together with SC in the HOD regime [2]. However, details remain unclear because of predominant effects of the Pr³⁺ moment on the μSR spectra.

To clarify the relationship between the Cu-spin correlation and SC in the electron-doped cuprates, we performed transport and μSR measurements of electron-doped La_2-xCe_xCuO₄ (LCCO) without rare-earth moments. Thin films of overdoped LCCO fabricated on the SrTiO₃ substrate by the pulsed-laser deposition method using a third harmonic of Nd:YAG laser (wavelength : 355 nm). μSR measurements using low-energy muons were performed at the Paul Scherrer Institut in Switzerland.

It was found that the Cu-spin correlation was developed at low temperatures for x = 0.17 where SC was almost suppressed. The development of the Cu-spin correlation at x = 0.17 may be related to a recently proposed ferromagnetic order [3].

[1] M. Fujita et al., Phys. Rev. Lett. 101, 107003 (2008).

[2] M. A. Baqiya et al., Phys. Rev. B 100, 064514 (2019).

[3] T. Sarkar et al., Science 368, 532 (2020).