Magnetism, heat capacity, and electronic structure of EuCd2P2 in view of its colossal magnetoresistance

The mechanism of the peculiar transport properties around the magnetic ordering temperature of semiconducting antiferromagnetic ${\mathrm{EuCd}}_{2}{\mathrm{P}}_{2}$ is not yet understood. With a huge peak in the resistivity observed above the N\'eel temperature ${T}_{\mathrm{N}}=10.6\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, it exhibits a colossal magnetoresistance effect. Recent reports on observations of ferromagnetic contributions above ${T}_{\mathrm{N}}$ as well as metallic behavior below this temperature have motivated us to perform a comprehensive characterization of this material, including its resistivity, heat capacity, magnetic properties, and electronic structure. Our transport measurements revealed quite different temperature dependence of resistivity with the maximum at 14 K instead of previously reported 18 K. Low-field susceptibility data support the presence of static ferromagnetism above ${T}_{\mathrm{N}}$ and show a complex behavior of the material at small applied magnetic fields. Namely, signatures of reorientation of magnetic domains are observed up to $T=16$ K. Our magnetization measurements indicate a magnetocrystalline anisotropy which also leads to a preferred alignment of the magnetic clusters above ${T}_{\mathrm{N}}$. The momentum-resolved photoemission experiments at temperatures from 24 down to 2.5 K indicate the permanent presence of a fundamental band gap without change of the electronic structure when going through ${T}_{N}$ that is in contradiction with previous results. We performed ab initio band structure calculations which are in good agreement with the measured photoemission data when assuming an antiferromagnetic ground state. Calculations for the ferromagnetic phase show a much smaller band gap, indicating the importance of possible ferromagnetic contributions for the explanation of the colossal magnetoresistance effect in the related ${\mathrm{EuZn}}_{2}{\mathrm{P}}_{2}$.