Tuning the Hall coefficient in single crystals of the heavy fermion compound YbNi₂B₂C by annealing

We present temperature-dependent magnetotransport measurements on as-grown and annealed YbNi₂B₂C single crystals. Annealing causes drastic changes in the Hall coefficient, R_H(T). Whereas for as-grown samples the Hall coefficient is negative between room temperature and 2 K, with a pronounced minimum at ≈22 K, for the samples annealed at 950 °C for 150 h, R_H(T) changes its sign twice in the same temperature range: from negative to positive on cooling below ∼100 K and back to negative below ∼10 K, and has a clear maximum at ≈45 K. Intermediate temperature dependencies can be achieved by reducing the annealing time. These findings are discussed within the framework of an annealing dependence of the skew scattering in conjunction with the recent structural, thermodynamic and transport studies of the effects of annealing in YbNi₂B₂C.