Spin correlation in trigonal EuMn${}_2$As${}_2$

Abstract

The trigonal structure of EuMn${}_2$As${}_2$ is an anomaly in the tetragonal 122-type pnictide family. We report detailed investigation of the underlying magnetic correlations in single crystal EuMn${}_2$As${}_2$ using high resolution elastic neutron scattering measurements. The system undergoes through two successive antiferromagnetic transitions at $T$ = 135 K and 14.4 K, respectively. Numerical modeling of the experimental data reveals the long range antiferromagnetic correlation of Mn-ions in the $a-b$ plane below $T_{N}1$ = 135 K. Mn spins are aligned closer to the diagonal axis of the unit cell. The lower temperature transition, below $T_{N}2$ = 14.4 K, is found to arise due to the long range antiferromagnetic correlation of Eu spins that are rotated by $\theta$ = 55 degree from the $c$-axis of the unit cell.

5 pages, 4 figures