Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 45: Correlated Electrons: Poster Session

TT 45.5: Poster

Donnerstag, 29. März 2012, 15:00–19:00, Poster B

Quantum Criticality in Ta(Fe_1−xV_x)₂ Probed by ⁵¹ V NMR and Magnetization — •Panchanana Khuntia, Michael Baenitz, Manuel Brando, Alexander Kerkau, Guido Kreiner, and Frank Steglich — Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.

Itinerant 3d weak ferromagnets like e.g. NbFe₂ or MnSi are tunable towards a (quantum) critical regime by doping, external pressure or magnetic field. The vicinity of a QCP leads to non Fermi liquid (NFL) behavior manifested by scaling laws in bulk properties like magnetization M(T), resistivity ρ(T) and specific heat C(T). In NMR, NFL phenomena are associated with non-Korringa like features in spin lattice relaxation rate (1/T₁) for T→0. We focus on NMR investigations on polycrystalline Ta(Fe_1−xV_x)₂ (x = 0.02, 0.05, 0.2 , 0.3) samples. For x = 0.02, the magnetic properties are reminiscent of itinerant FM at the verge of a FM instability with enhanced M(T→0) indicating FM fluctuations. ⁵¹V NMR spectra are broadened inhomogeneously at low temperatures with considerable shift which reflects the hyperfine coupling of itinerant 3d moments with the ⁵¹V nuclei.⁵¹(1/T₁T) violates the Korringa law and exhibits a T^−0.8 dependence for small fields which is a signature of critical fluctuations. The value of the Korringa product(<1) indicates FM correlations between itinerant moments. Further doping the system undergoes AFM ordering up to x=0.3, where a simple paramagnetic behavior is observed. Ta(Fe_1−xV_x)₂ is of special interest because FM critical fluctuations evolve in the proximity of an AFM state by nominal V doping.