NMR Search for the Spin Nematic State in a LaFeAsO Single Crystal

Fu, Morgan; Torchetti, David; Imai, Takashi; Ning, Fanlong; Yan, Jiaqiang; Sefat, Athena S.

doi:10.1103/physrevlett.109.247001

Cited by 89 publications

(88 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…3) shows a jump on passing from just above T m ( 75 As NQR) to below T m ( 75 As ZF-NMR) which is very similar to the one detected [45] in LaFeAsO. This abrupt change in ν Q is associated with the T-O distortion.…”

supporting

confidence: 57%

Fast recovery of the stripe magnetic order by Mn/Fe substitution in F-doped LaFeAsO superconductors

et al. 2017

View full text Add to dashboard Cite

75 As Nuclear Magnetic (NMR) and Quadrupolar (NQR) Resonance were used, together with Mössbauer spectroscopy, to investigate the magnetic state induced by Mn for Fe substitutions in F-doped LaFe1−xMnxAsO superconductors. The results show that 0.5% of Mn doping is enough to suppress the superconducting transition temperature Tc from 27 K to zero and to recover the magnetic structure observed in the parent undoped LaFeAsO. Also the tetragonal to orthorhombic transition of the parent compound is recovered by introducing Mn, as evidenced by a sharp drop of the NQR frequency. The NQR spectra also show that a charge localization process is at play in the system. Theoretical calculations using a realistic five-band model show that correlation-enhanced RKKY exchange interactions between nearby Mn ions stabilize the observed stripe magnetic order. These results give compelling evidence that F-doped LaFeAsO is a strongly correlated electron system at the verge of an electronic instability.PACS numbers: 74.70. Xa, 76.75.+i, 74.40.Kb, 74.20.Mn The interplay between impurity induced disorder and electronic correlations often gives rise to complex phase diagrams in condensed matter [1, 2]. The electronic correlations drive a system towards a quantum phase transition, as it is typically found in the fullerides [3] and in heavy-fermion compounds [4, 5], with an enhancement of the local susceptibility and, hence, a small perturbation, as the one associated with a tiny amount of impurities, can significantly affect the electronic ground-state [6][7][8][9]. In the cuprates and in the electron-doped iron-based superconductors (IBS) the strength of the electronic correlations can be tuned either by charge doping or by applying an external or a chemical pressure. [10][11][12][13][14] In particular, upon increasing the charge doping, the strength of the electronic correlations tend to decrease [15][16][17][18][19][20][21][22] and a metallic Fermi liquid (FL) ground state is usually restored [23][24][25][26][27]. However significant electronic correlations may still be present even close to the charge doping levels yielding the maximum superconducting transition temperature T c and a convenient method to test their magnitude is to perturb the system with impurities.The introduction of Mn impurities at the Fe sites was reported to strongly suppress T c in several IBS, both of the BaFe 2 As 2 [28-30] and of the LnFeAsO (Ln1111, Ln=Lanthanides) [31] families. Within the Ln1111 family the effect of impurities is particularly significant in La1111 [27,32]. In fact, while in most the IBS compounds the T c suppression rate (dT c /dx) is well below 10 K/% Mn, in LaFeAsO 0.89 F 0.11 just 0.2 -0.3% of Mn impurities suppress superconductivity from the optimal T c 27 K (dT c /dx ∼ 110 K/% Mn) and then, at higher Mn doping levels, a magnetic order develops (see Fig. 1b) [32][33][34]. The understanding of why such a dramatic effect is present, what type of magnetic order is developing and how to describe these materials at the microscopic level ...

show abstract

supporting

confidence: 57%

Fast recovery of the stripe magnetic order by Mn/Fe substitution in F-doped LaFeAsO superconductors

et al. 2017

View full text Add to dashboard Cite

show abstract

“…These results are in strong contrast to LaFeAsO, where R ab nearly doubles [29] and R ac increases strongly from ≈ 1. T N .…”

contrasting

confidence: 41%

Origin of the Tetragonal-to-Orthorhombic Phase Transition in FeSe: A Combined Thermodynamic and NMR Study of Nematicity

et al. 2015

View full text Add to dashboard Cite

The nature of the tetragonal-to-orthorhombic structural transition at Ts ≈ 90 K in single crystalline FeSe is studied using shear-modulus, heat-capacity, magnetization and NMR measurements. The transition is shown to be accompanied by a large shear-modulus softening, which is practically identical to that of underdoped Ba(Fe,Co)2As2, suggesting very similar strength of the electronlattice coupling. On the other hand, a spin-fluctuation contribution to the spin-lattice relaxation rate is only observed below Ts. This indicates that the structural, or "nematic", phase transition in FeSe is not driven by magnetic fluctuations.PACS numbers: 74.70. Xa, 74.25.Bt, 74.25.Ld, 74.25.nj One of the most intriguing questions in the study of iron-based superconductors concerns the relation between structure, magnetism and superconductivity [1][2][3][4][5][6][7][8][9][10]. Stripe-type antiferromagnetic order often occurs at the same or at a slightly lower temperature than the tetragonal-to-orthorhombic structural distortion and the two types of order are closely related by symmetry. They break the four-fold rotational symmetry of the high-temperature phase, which can be associated with a nematic degree of freedom [4,6]. Superconductivity typically is strongest around the point where the structural transition (T s ) and the antiferromagnetic transition (T N ) are suppressed by pressure or chemical substitution. Whether the magnetic or the structural instability is the primary one, is still under intense debate [10], also because of its relevance to the pairing mechanism [5,6]. Recently, scaling relations between the shear modulus related to the structural distortion, C 66 , and the spinlattice relaxation time T 1 as a measure of the strength of spin fluctuations, have been proposed [7,8] in order to address the above question. They were found to be well satisfied in the Ba(Fe,Co) 2 As 2 system [7,8], where T s and T N are in close proximity to each other, suggesting a magnetically-driven structural transition [7]. Clearly, it is of great interest to see if a relation between shear modulus and spin fluctuations is universally observed in other iron-based materials.FeSe is structurally the simplest iron-based superconductor and has attracted a lot of attention because of a nearly four-fold increase of its T c ≈ 8 K under pressure [11]. Moreover, this system is particularly interesting with respect to the relation of structure and magnetism, since it undergoes a tetragonal-to-orthorhombic structural phase transition at T s ∼ 90 K, similar to that found in the 1111-and 122-type parent compounds [2], but does not order magnetically at ambient pressure [12,13]. Spin fluctuations at low temperatures were, however, observed in nuclear magnetic resonance (NMR) measurements [14]. Surprisingly, the orthorhombic distortion of FeSe is not reduced upon entering the superconducting state [9] in strong contrast to underdoped BaFe 2 As 2 [3,15], indicating different couplings between structure and superconductivity. This strongly motivates fu...

show abstract

“…However, recent NMR studies of LaFeAsO below the structural transition at 156 K show a cessation of the growth of orthorhombic domains by 120 K and present evidence for the emergence of a spin nematic phase. 9 The low temperature upturn in M/H (see Fig. 2) has been reported numerous times and is typically attributed to paramagnetic impurities.…”

Section: Resultsmentioning

confidence: 99%

“…3 This interest is primarily driven by the correlated electron phenomena these compounds display such as high-T c superconductivity, commensurate and incommensurate spin-density wave order, and the interplay of these phenomena, as well as structural transitions and pressure-induced isostructural volume collapses. [4][5][6][7][8][9][10] The highest T c 's among the iron pnictide superconductors have been found in the arsenide 1111 compounds, such as Gd 1−x Th x FeAsO with an onset of T c = 56 K when x = 0. 20.…”

Section: Introductionmentioning

confidence: 99%

Magnetotransport properties of single-crystalline LaFeAsO

et al. 2013

View full text Add to dashboard Cite

Measurements of magnetization, specific heat, electrical resistivity, Hall effect, and magnetoresistance on single crystalline samples of LaFeAsO grown in a NaAs flux are reported. While this material is known to be a semimetal, the temperature dependence of the electrical resistivity data presented herein is reminiscent of semiconducting behavior and exhibits distinct features associated with a structural transition and spin density wave (SDW) order. Magnetoresistance and Hall coefficient measurements were performed in magnetic fields up to 9 T applied perpendicular to the basal plane using a van der Pauw configuration. The charge carrier density and mobility indicate that electrons are the majority charge carriers and exhibit features indicative of the structural transition and SDW formation. Low temperature X-ray diffraction measurements have confirmed that the structural transition in these samples occurs near 140 K, compared to a transition temperature of 156 K observed in polycrystalline samples. Isotherms of magnetoresistivity measured as a function of magnetic field can be scaled onto a single curve in which the scaling field is a linear function of temperature between 2.2 K and 180 K.

show abstract

NMR Search for the Spin Nematic State in a LaFeAsO Single Crystal

Cited by 89 publications

References 34 publications

Fast recovery of the stripe magnetic order by Mn/Fe substitution in F-doped LaFeAsO superconductors

Fast recovery of the stripe magnetic order by Mn/Fe substitution in F-doped LaFeAsO superconductors

Origin of the Tetragonal-to-Orthorhombic Phase Transition in FeSe: A Combined Thermodynamic and NMR Study of Nematicity

Magnetotransport properties of single-crystalline LaFeAsO

Contact Info

Product

Resources

About