Hall effect anomaly and low-temperature metamagnetism in the Kondo compound CeAgBi2

Abstract

Heavy fermion (HF) materials exhibit a rich array of phenomena due to the strong Kondo coupling between their localized moments and itinerant electrons. A central question in their study is to understand the interplay between magnetic order and charge transport, and its role in stabilizing new quantum phases of matter. Particularly promising in this regard is a family of tetragonal intermetallic compounds CeTX2 (where T denotes transition metal and X denotes pnictogen), which includes a variety of HF compounds showing T-linear electronic specific heat C-e similar to gamma T, with gamma similar to 20-500 mJ mol(-1) K-2, reflecting an effective-mass enhancement ranging from small to modest. Here, we study the low-temperature field-tuned phase diagram of high-quality CeAgBi2 using magnetometry and transport measurements. We find an antiferromagnetic transition at T-N = 6.4K with weak magnetic anisotropy and the easy axis along the c axis, similar to previous reports (T-N = 6.1K). This scenario, along with the presence of two anisotropic Ruderman-Kittel-Kasuya-Yosida interactions, leads to a rich field-tuned magnetic phase diagram, consisting of five metamagnetic transitions of both first and second order. In addition, we unveil an anomalous Hall contribution for fieldsH < 54 kOe, which is drastically altered when H is tuned through a trio of transitions at 57, 78, and 84 kOe, suggesting that the Fermi surface is reconstructed in a subset of the metamagnetic transitions.