Understanding the giant resistivity peak and negative magnetoresistance in EuCd₂P₂

Colossal negative magnetoresistance (CMR) has been observed in various Eu-based Zintl compounds, a outstanding example is EuCd₂P₂. Several different mechanisms such as spin fluctuations [1], strong spin-carrier interactions [2], BKT transition [3] and band reconstruction [4] were predicted to be involved in producing CMR in EuCd₂P₂. Here we report observation of two different kinds of high temperature resistivity behaviors, an insulating trend and a bad metallic trend in different samples of EuCd₂P₂. Samples which display an insulating trend show very large resistivity peak happening at a lower temperatures compared to bad metallic samples. We present the heat capacity, magnetoresistance and carrier concentration data comparing these two samples. We also report a very large non-linear Hall effect and an intriguing non-linear transport behavior in this compound. Our results can shed light on the microscopic mechanism of CMR in EuCd₂P₂.