Annealing-tuned Hall coefficient in single crystals of the YbNi$_2$B$_2$C heavy fermion

TL;DR

This study investigates how annealing affects the temperature-dependent Hall coefficient in YbNi₂B₂C single crystals, revealing significant sign changes and maxima that relate to skew scattering and structural modifications.

Contribution

It provides new insights into the annealing-induced modifications of the Hall effect in heavy fermion crystals, highlighting the role of skew scattering and structural changes.

Findings

Annealing causes the Hall coefficient to change sign twice.

The Hall coefficient exhibits a maximum at approximately 45 K after annealing.

Intermediate annealing times produce intermediate temperature dependencies.

Abstract

We present temperature-dependent magneto-transport measurements on as-grown and annealed YbNi$_2$B$_2$C 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 {\it minimum} at $\approx 22$ K, for the samples annealed at $950^\circ$ C for 150 hours, $R_H(T)$ changes its sign twice in the same temperature range: from negative to positive on cooling below $\sim 100$ K and back to negative below $\sim 10$ K, and has a clear {\it maximum} at $\approx 45$ 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 YbNi$_2$B$_2$C.