Copper-substituted iron telluride: A phase diagram

Abstract

We have studied the structure, magnetic, and transport properties of copper substituted iron telluride. Our results extend the range of copper substitution to 60% substitution per formula unit, which is far beyond previously stated solubility limits. Substitution of copper into antiferromagnetic iron telluride is found to suppress the signatures of the low-temperature transitions in susceptibility and resistance measurements, giving rise to an insulating, spin glass state. Upon increasing the copper substitution from 4% to 6%, short range antiferromagnetic order appears followed by the combined magnetic and structural transition at a lower temperature, although the magnetic order is ultimately not resolution limited with a correlation length of 250 Å in the 6% Cu-substituted sample, in contrast to the magnetic order of the 4% copper substituted sample, which is resolution limited. Upon warming the 6% Cu-substituted sample in the presence of a 5 T magnetic field oriented along the b axis, magnetic and structural phase transitions are observed at a temperature much lower than those of the magnetic and structural transitions which occur in zero field. Furthermore, these transitions are absent upon cooling in this field. We discuss the field results in the most general terms possible, including possible random field effects.

Local breaking of fourfold rotational symmetry by short-range magnetic order in heavily overdoped Ba(Fe1−xCux)2As2Wang1, Song2, Hu3 et al. 2017Phys. Rev. B112101View full textAdd to dashboardCite

“…SG behavior seen in magnetization measurements is also reported for other heavily Cu-doped iron pnictides [10,16] and chalcogenides [19][20][21][22], pointing to the possible presence of shortrange magnetic order. Importantly, in both A(Fe 1−x Cu x ) 2 As 2 and NaFe 1−x Cu x As where SG behavior is observed, doped Cu is in a nonmagnetic 3d 10 configuration [10,18] and therefore any SG or short-range magnetic order must be due to Fe.…”

“…1(c). The separation between ZFC and FC susceptibilities occurring at low temperatures indicates SG-like behavior, similar to other heavily Cu-doped iron pnictides and chalcogenides [10,16,[19][20][21][22].…”

“…The robustness of stripe-type magnetism suggests it is an inherent instability of the FeAs-plane and may be the driving force of physics in iron pnictides. Given similar susceptibility and transport behaviors seen in several other Cu-doped iron pnictide and chalcogenide systems [10,[19][20][21][22], it is probable that stripe-type short-range magnetic order is also present in those systems.…”

“…With increasing Cu concentration (x 10%), insulating-like transport and short-range magnetic order develop, evolving towards an insulator with long-range magnetic order and Fe-Cu ordering near x ≈ 50% [18]. The evolution from * Yu.Song@rice.edu † pdai@rice.edu metallic to insulating/semiconducting transport is also observed in Ba(Fe 1−x Cu x ) 2 As 2 (x 0.145), Sr(Fe 1−x Cu x ) 2 As 2 (x 0.06) [10], Fe 1.01−x Cu x Se (x 0.03) [19,20], and Fe 1+δ−x Cu x Te (x 0.06) [21,22]. The insulating transport in NaFe 1−x Cu x As is a result of electron correlations [18,23] facilitated by the ordering of Fe and Cu into quasi-onedimensional (1D) chains [18].…”

The influence of magnetic order on the magnetoresistance anisotropy of Fe1 + δ–xCuxTe

“…A slight amount of copper substitution into Fe 1.1 Te, making Fe 1.1−x Cu x Te, has been shown to suppress (concomitantly) the magnetic and structural phase transition temperatures [19][20][21][22][23] while the magnetic order remains long-range and commensurate at x = 0.04 [23]. At x = 0.1, only short-range incommensurate magnetism exists and no structural transition is observed by neutron diffraction [20].…”