Local atomic and magnetic structure of dilute magnetic semiconductor (Ba,K)(Zn,Mn)$_2$As$_2$

TL;DR

This study investigates the atomic and magnetic structures of the dilute magnetic semiconductor (Ba,K)(Zn,Mn)$_2$As$_2$ using advanced scattering techniques, revealing local structural distortions and ferromagnetic correlations that persist above the ordering temperature.

Contribution

It provides new insights into the local atomic environment and magnetic correlations in (Ba,K)(Zn,Mn)$_2$As$_2$, highlighting the coexistence of local orthorhombic structures and ferromagnetic spin alignment.

Findings

Detection of a change in unit cell volume curvature at ferromagnetic transition temperature.

Existence of a local orthorhombic structure on a short length scale.

Ferromagnetic alignment of Mn spins along the c-axis with correlations above the transition temperature.

Abstract

We have studied the atomic and magnetic structure of the dilute ferromagnetic semiconductor system (Ba,K)(Zn,Mn)$_2$As$_2$ through atomic and magnetic pair distribution function analysis of temperature-dependent x-ray and neutron total scattering data. We detected a change in curvature of the temperature-dependent unit cell volume of the average tetragonal crystallographic structure at a temperature coinciding with the onset of ferromagnetic order. We also observed the existence of a well-defined local orthorhombic structure on a short length scale of $\lesssim 5$ \AA, resulting in a rather asymmetrical local environment of the Mn and As ions. Finally, the magnetic PDF revealed ferromagnetic alignment of Mn spins along the crystallographic $c$-axis, with robust nearest-neighbor ferromagnetic correlations that exist even above the ferromagnetic ordering temperature. We discuss these results in the context of other experiments and theoretical studies on this system.