Magnetic Field Effect on the Static Antiferromagnetism of the Electron-Doped SuperconductorPr1−xLaC

Abstract

Effects of magnetic fields (applied along the c-axis) on static spin correlation were studied for the electron-doped superconductors Pr1−xLaCexCuO4 with x=0.11 (Tc=26 K) and x=0.15 (Tc=16 K) by neutron scattering measurements. In the x=0.11 sample located near the antiferromagnetic(AF) and superconducting phase boundary, the field dependence of both the magnetic intensity at T=3 K and the onset temperature of the magnetic order exhibits a peak at ∼5 T. In contrast, in the overdoped x=0.15 sample a static AF order is neither observed at zero-field nor induced by the field up to 8.5 T. Difference and similarity of the field effect between the hole-and electron-doped high-Tc cuprates are discussed.PACS numbers: 74.72. Jt, 74.25.Ha, 75.50.Ee, 61.12.Ld Magnetism in lamellar copper oxides is widely believed to play an important role in the mechanism of high-T c superconductivity [1]. Extensive neutron scattering measurements have indeed shown an intimate relation between incommensurate (IC) low-energy spin fluctuations observed in the hole-doped (p-type) La 2−x Sr x CuO 4 (LSCO) [2,3,4] and their superconductivity [5]. Recentlly, neutron scattering study on the superconducting (SC) LSCO with x∼1/8 and excess-oxygen doped La 2 CuO 4+y revealed an enhancement of the long-ranged IC magnetic order by magnetic fields applied along the c-axis [6,7,8,9]. Lake et al., furthermore, found field-induced slow spin fluctuations below a spin-gap energy, which shows a tendency toward the magnetic order, in the optimally doped LSCO [10]. These authors discussed that the antiferromagnetic (AF) insulator with IC correlations is a possible ground state after vanishing the superconductivity, as supported by theoretical studies [11,12,13]. Thus, in order to clarify the universal nature of magnetism hidden behind the superconductivity, it is necessary to investigate whether the AF order is commonly observed by suppressing the superconductivity.Important challenges have been made on the prototypical electron-doped (n-type) system of Nd 2−x Ce x CuO 4 (NCCO) which shows commensurate spin fluctuations at the tetragonal (1/2 1/2 0) reciprocal-lattice position in both AF and SC phases [14]. In Nd 1.86 Ce 0.14 CuO 4 , at least down to 15 K Matsuda et al. observed no field effect on the AF order which coexists or phase separates with the bulk superconductivity[15] , whereas Kang et al. subsequently reported a field-enhanced huge magnetic intensity for Nd 1.85 Ce 0.15 CuO 4 and asserted the AF order as a competing ground state with the superconductivity, irrespective of carrier type [16]. This discrepancy could be originated from drastic(first-order like) doping dependence of the static magnetism near the boundary between AF and SC phases [17,18]. However, since the bulk superconductivity with identical T c of 26 K as well as the AF order appears in both samples, field-effects on the AF order and the superconductivity are still controversial. Furthermore, a effect on Nd 3+ spins is expected to be significant in NCCO, and therefore, the results ...

Electronically competing phases and their magnetic field dependence in electron-doped nonsuperconducting and superconductingPr0.88LaCe0.12CuO4±δ

“…15͑a͒ and 15͑e͔͒, consistent with an earlier report on an overdoped PLCCO ͑T c =16 K͒. 48 Note that in this case the peaks at both positions arise mostly from superlattice and ͑Pr, La, Ce͒ 2 O 3 and there are no static AF orders in the sample ͓Figs. 6͑a͒ and 6͑b͔͒.…”

“…Electron-doped Pr 1−x LaCe x CuO 4±␦ , where Pr 3+ has a singlet ground state 47 and La is nonmagnetic, is ideal for this purpose. Using single crystals of Pr 1−x LaCe x CuO 4±␦ with x = 0.11 ͑T c =16 K͒ and x = 0.15 ͑T c =26 K͒, Fujita et al 48 found that a c-axis-aligned magnetic field enhances the residual AF order in the x = 0.11 sample at ͑0.5,1.5,0͒ position, but has no effect in the overdoped x = 0.15 sample. The authors conclude that a c-axis field changes both the magnetic intensity and the onset of the Néel ordering temperature T N for the x = 0.11 sample, with the maximum field effect at ϳ5 T. 48 Our approach to this problem has been slightly different from that of Fujita et al 48 Instead of preparing different SC Pr 1−x LaCe x CuO 4±␦ samples as a function of Ce doping, we grew single crystals of PLCCO using a traveling solvent floating zone furnace.…”

Quantum spin correlations through the superconducting-to-normal phase transition in electron-doped superconducting Pr 0.88 LaCe 0.12 CuO 4-δ

“…Although previous muon spin relaxation measurements have observed the emergence of field-induced AF order throughout the volume of optimally doped PLCCO (26), neutron diffraction experiments have failed, possibly because of insufficient sample volume, to detect such a signal for optimally and overly doped PLCCO (27,28). Because our PLCCO samples have no observable static AF order above T ϭ 0.6 K (8), we would expect the observed peak at (1/2, 1/2, 0) in Fig.…”

Muon spin rotation studies of electronic excitations and magnetism in the vortex cores of superconductors

“…Fujita et al used neutrons to study the same Pr 1−x LaCe x CuO 4 samples that Kadono et al investigated with µSR [168]. In zero field, weak AF order was detected in the x = 0.11 sample, in contrast to ZF-µSR measurements that found only random magnetism due to small Pr moments [169].…”