Quantum magnetoresistance of the PrFeAsO oxypnictide

Abstract

We report the observation of an unusual B dependence of transverse magnetoresistance (MR) in the PrFeAsO, one of the parent compound of pnictide superconductors. Below the spin density wave transition, MR is large, positive and increases with decreasing temperature. At low temperatures, MR increases linearly with B up to 14 T. For T ≥40 K, MR vs B curve develops a weak curvature in the low-field region which indicates a crossover from B linear to B 2 dependence as B→0. The B linear MR originates from the Dirac cone states and has been explained by the quantum mechanical model proposed by Abrikosov.The Fe-pnictide high-temperature superconductors have attracted much interest because of the interplay of multi-band structure of Fermi surface and antiferromagnetism mediated by the magnetic Fe ions 1 . The undoped compounds RFeAsO (R=La, Ce, Pr, Nd and Sm) and AFe 2 As 2 (A=Ba, Ca, Sr, Eu) are semimetal and exhibit a structural phase transition at T S followed by an antiferromagnetic spin-density wave (SDW) magnetic ordering at T N 2 . This SDW has been argued to arise from Fermi surface nesting of the hole and electron Fermi surface sheets, and/or from one-electron band effects 3 . The theoretical calculation shows that the combination of the physical symmetry and topology of the band structure naturally stabilizes a gapless nodal SDW state with Dirac nodes for the parent compounds of pnictide 4,5 . Angle-resolved photoemission spectroscopy measurement on BaFe 2 As 2 confirms a Dirac-type dispersion in the antiferromagnetic phase 6 .Dirac type dispersion was first observed in graphene, where the energy spectrum is linear in momentum at the corners of the first Brillouin zone, so that the electrons at low energies can be described by the Dirac equation 7,8 . Such a unique energy band structure gives rise to several characteristic transport properties 9 . In this letter, we report the investigation on the magnetotransport properties of PrFeAsO sample, one of the parent compound of 1111 oxypnictides. We observe a large positive magnetoresistance (MR) below the SDW transition temperature. At low temperature, the MR follows a linear field dependence up to 14 T magnetic field. For T ≥40 K, MR vs B curve develops a weak curvature in the lowfield region which indicates a crossover from B linear to B 2 dependence. The B linear dependence of MR is analyzed by the quantum mechanical model developed by Abrikosov 10,11 .Polycrystalline PrFeAsO sample has been prepared by standard solid state reaction method as described in our a) Electronic mail: dilipkumar.bhoi@saha.ac.in b) Electronic mail: prabhat.mandal@saha.ac.in earlier reports 12 . The phase purity of the sample was checked by powder X-ray diffraction method and no trace of the impurity phase has been detected. The scanning electron microscope (SEM) (SUPRA, 35 VP, Carl Zeiss) image reveals well connected platelet crystallites. The energy dispersive X-ray spectra obtained from grains of different size and morphology reveal that the stoichiometric ratio Pr:Fe:As:O is close t...

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“…4) -like MR observed in Fe1.02Te ( Fig. 6(a)), but looks similar to what has been observed in iron pnictides [55][56][57] , where the linear field dependence of MR is attributed to Dirac cone states 58 . This observation implies that the …”

Anomalous magnetism of Pr in PrCoAsO

“…In case of Fe counter part of PrCoAsO, i.e., PrFeAsO, a 12 K resistivity step is reported earlier in resistivity data and was assigned to the unusual ordering of Pr moments due to Pr 4f and Fe 3d interaction. 12,16 The issue here is that PrCoAsO behaves more closely like LaCoAsO than the magnetic Sm/NdCoAsO. This is intriguing because unlike non magnetic La, Pr must behave more closely like the magnetic Nd and Sm counterparts.…”

Multiband effects and possible Dirac fermions inFe1+yTe0.6Se0.4Sun1, Taen2, Yamada3 et al. 2014Phys. Rev. B618481View full textAdd to dashboardCite

“…[5][6][7][8] Moreover, a Dirac cone state, coming from the nodes of the spin-density-wave (SDW) gap by complex zone folding in different bands, is observed in Ba/SrFe 2 As 2 and La/PrFeAsO. [9][10][11][12][13] Although the weight of Dirac cone state is small, it can dominate the transport properties because of its extremely high mobility. In consequence, a large and linear temperature dependent MR was observed.…”