Pressure-dependence of the Colossal Magnetoresistance of Europium Cadmium Phosphate (EuCd₂P₂)

Europium Cadmium Phosphate (EuCd₂P₂) is a newly discovered strongly correlated electron system that exhibits colossal magnetoresistance (CMR) at ambient pressure. Colossal Magnetoresistance is an important material property that can have pleothra of applications in technology. It is generally assumed that CMR is a property intrinsic to manganese oxides with mixed valence and a cubic perovskite structure. However, the strong CMR seen in EuCd2P2 without manganese, oxygen or perovskite structures underscores a need for a more comprehensive theory of this phenomenon.

Pressure is an effective tool to tune the interactions in materials and allow testing the theoretical hypothesis. In the case of EuCd₂P₂, it is known that the observed peak in the temperature dependence of the electrical resistivity occurs right above its neel temperature where it transitions from a paramagnetic material to an A-type anti–ferromagnetic (AFM) material. Ambient pressure studies suggest that CMR in EuCd₂P₂ arises from spin fluctuations. By comparing the AC magnetic susceptibility and the electrical resistance of EuCd₂P₂ at the temperatures where the CMR is most prominent, direct evidence of this theory can be obtained. The application of pressure brings the atomic planes closer and their interactions directly contribute to the magnetic state of the EuCd₂P₂.

In this study, we have investigated the AC magnetic susceptibility of EuCd₂P₂ as a function of pressure and temperature in a Diamond Anvil Cell (DAC) device. Measuring magnetic susceptibility provides valuable insights to the magnetic behavior and electron correlation properties of a material.Diamond Anvil Cell (DAC) allows achieving the highest static pressure conditions and is compatible with operation at low temperatures. However, due to very small sample size in a typical DAC experiment magnetic susceptibility experiments are extremely challenging. In this study, we present the method of construction of the experimental setup for such measurements, the difficulties associated with obtaining an acceptable signal-to-background ratio, techniques of calibration and data analysis. Future work will include the findings that will help enhance our current understanding of CMR and the unique properties associated with EuCd₂P₂.