Itinerant and local-moment magnetism in EuCr2As2 single crystals

TL;DR

This study characterizes EuCr2As2's crystal structure, magnetic properties, and electronic structure, revealing ferromagnetic Eu moments below 21 K and a predicted antiferromagnetic order of Cr, with implications for understanding its magnetic interactions.

Contribution

It provides comprehensive experimental and theoretical insights into the magnetic and electronic properties of EuCr2As2, including magnetic ordering and electronic structure predictions.

Findings

Eu moments order ferromagnetically below 21 K

Cr sublattice predicted to have G-type antiferromagnetic order

Electronic structure indicates unstable nonmagnetic Cr state

Abstract

We report on the crystal structure, physical properties, and electronic structure calculations for the ternary pnictide compound EuCr2As2. X-ray diffraction studies confirmed that EuCr2As2 crystalizes in the ThCr2Si2-type tetragonal structure (space group I4/mmm). The Eu ions are in a stable divalent state in this compound. Eu moments in EuCr2As2 order magnetically below Tm = 21 K. A sharp increase in the magnetic susceptibility below Tm and the positive value of the paramagnetic Curie temperature obtained from the Curie-Weiss fit suggest dominant ferromagnetic interactions. The heat capacity exhibits a sharp {\lambda}-shape anomaly at Tm, confirming the bulk nature of the magnetic transition. The extracted magnetic entropy at the magnetic transition temperature is consistent with the theoretical value Rln(2S+1) for S = 7/2 of the Eu2+ ion. The temperature dependence of the electrical resistivity \r{ho}(T) shows metallic behavior along with an anomaly at 21 K. In addition, we observe a reasonably large negative magneto-resistance (~ -24%) at lower temperature. Electronic structure calculations for EuCr2As2 reveal a moderately high density of states of Cr-3d orbitals at the Fermi energy, indicating that the nonmagnetic state of Cr is unstable against magnetic order. Our density functional calculations for EuCr2As2 predict a G-type AFM order in the Cr sublattice. The electronic structure calculations suggest a weak interlayer coupling of the Eu moments.