Magnetic behavior of EuCu2As2: Delicate balance between antiferromagnetic and ferromagnetic order

TL;DR

This study investigates EuCu2As2, revealing a delicate balance between antiferromagnetic and ferromagnetic order, with evidence of magnetic fluctuations and field-induced spin reorientation near 15-20 K.

Contribution

It provides detailed experimental insights into the competing magnetic interactions and field effects in EuCu2As2, highlighting the coexistence and transition between magnetic states.

Findings

Eu is divalent and orders antiferromagnetically below 15 K.

An upturn in magnetic susceptibility occurs just below 20 K, indicating ferromagnetic tendencies.

A small magnetic field induces spin reorientation in the antiferromagnetic state.

Abstract

The Eu-based compound, EuCu2As2, crystallizing in the ThCr2Si2-type tetragonal structure, has been synthesized and its magnetic behavior has been investigated by magnetization (M), heat-capacity (C) and electrical resistivity (rho) measurements as a function of temperature (T) and magnetic field (H) as well as by 151Eu Moessbauer measurements. The results reveal that Eu is divalent ordering antiferromagnetically below 15 K in the absence of magnetic field, apparently with the formation of magnetic Brillouin-zone boundary gaps. A fascinating observation is made in a narrow temperature range before antiferromagnetism sets in: That is, there is a remarkable upturn just below 20 K in the plot of magnetic susceptibility versus T even at low fields, as though the compound actually tends to order ferromagnetically. There are corresponding anomalies in the magnetocaloric effect data as well. In addition, a small application of magnetic field (around 1 kOe at 1.8 K) in the antiferromagnetic state causes spin-reorientation effect. These results suggest that there is a close balance between antiferromagnetism and ferromagnetism in this compound