Disordered magnetism in superconducting KFe2As2 single crystals

Abstract

High-quality KFe2As2 (K122) single crystals synthesized by different techniques have been studied by magnetization and specific heat (SH) measurements. There are 2 types of samples both affected by disordered magnetic phases: (i) cluster-glass (CG) like or (ii) Griffiths phase (G) like. For (i) at low applied magnetic fields the T-dependence of the zero field cooled (ZFC) linear susceptibility (chi_l) exhibits an anomaly with an irreversible behavior in ZFC and field cooled (FC) data. This anomaly is related to the freezing temperature T_f. The extrapolated T_f to B=0 varies between 50 K and 90 K. Below T_f we observed a magnetic hysteresis in the field dependence of the isothermal magnetization (M(B)). The frequency shift of the freezing temperature delta T_f=Delta T_f/[T_fΔ(\ln ν)]\sim 0.05$hasanintermediatevalue,whichprovidesevidencefortheformationofaCG-likestateintheK122samplesoftype(i).Thefrequencydependenceoftheir{T}_{f}followsaconventionalpower-lawdivergenceofcriticalslowingdown:tau=ta{u}_0[T_f(nu)/T_f(0)-1{]}^{-z{\nu }^{{}^{\prime }}}withthecriticalexponentz{\nu }^{{}^{\prime }}=10(2)andarelativelylongcharacteristictimeconstantta{u}_0=6.9x10^{-11}$s also supporting a CG behavior. The large value of the Sommerfeld coefficient was related to magnetic contribution from a CG. Samples from (ii) did not show a hysteresis behavior for chi_l(T) and M(B). Below a crossover temperature T^* sim 40 K a power-law dependence in the chi_l propto T^[lambda_G-1}], with a non-universal lambda_G was observed, suggesting a quantum G-like behavior. In this case chi_l and M(B) can be scaled using the scaling function M_s(T,B)= B^{1-λ_{\tiny G}}Y(mu B/k_BT) with the scaling moment mu of the order of 3.5mu_b. The same non-universal exponent was found also in SH measurements, where the magnetic contribution C/T propto T^(lambda_G-1).

6 pages, 6 figures

References in corpus (13)

• The Puzzle of High Temperature Superconductivity in Layered Iron Pnictides and Chalcogenides
• Superconductivity in Iron Compounds
• Non-Fermi liquid behavior and Griffiths phase in {\it f}-electron compounds
• Ferromagnetic cluster spin-glass behavior in PrRhSn3
• Quantum Griffiths effects and smeared phase transitions in metals: theory and experiment
• Spin-glass behavior in Ni-doped La1:85Sr0:15CuO4
• Quantum Griffiths Phase in the weak itinerant ferromagnetic alloy Ni${}_{1-x}$V${}_x$
• Specific heat and upper critical field in KFe2As2 single crystals
• Potential antiferromagnetic fluctuations in hole-doped iron-pnictide superconductor Ba_{1-x}K_{x}Fe_{2}As_{2} studied by ^{75}As nuclear magnetic
• 75As NMR study of single crystals of the heavily overdoped pnictide superconductors Ba{1-x}KxFe2As2 (x = 0.7 and 1)
• Specific heat in KFe2As2 in zero and applied magnetic field
• High pressure transport studies of the LiFeAs analogues CuFeTe2 and Fe2As
• Are there nodes in LaFePO, BaFe${}_2$(AsP)${}_2$, and KFe${}_2$As${}_2$ ?

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• Calorimetric study in single crystal of CsFe${}_2$As${}_2$
• Superconducting specific heat jump $\Delta C_{\mathrm{el}}\propto T_c^{\beta }(\beta \approx 2)$ for K${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$
• Evolution of London penetration depth with scattering in single crystals of K${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$
• Structure, magnetic and thermodynamic properties of heterometallic ludwigites: Cu2GaBO5 and Cu2AlBO5
• Superconducting properties of K${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$ under pressure
• Constraints on the total coupling strength to bosons in iron based superconductors
• Microscopic evidence for Fulde-Ferrel-Larkin-Ovchinnikov state and multiband effects in KFe${}_2$As${}_2$