Suppression of spin-density-wave transition and emergence of ferromagnetic ordering of Eu$^{2+}$ moments in EuFe$_{2-x}$Ni$_{x}$As$_{2}$

TL;DR

This study investigates how Ni doping in EuFe$_{2}$As$_{2}$ suppresses the spin-density-wave transition and induces a transition from antiferromagnetic to ferromagnetic ordering of Eu$^{2+}$ moments, without observing superconductivity.

Contribution

It provides a systematic analysis of magnetic and electronic phase evolution in EuFe$_{2-x}$Ni$_{x}$As$_{2}$, revealing the suppression of SDW and the magnetic transition change due to Ni doping.

Findings

SDW transition suppressed for x ≥ 0.16

Eu$^{2+}$ moments switch from AFM to FM for x ≥ 0.06

No superconductivity observed down to 2 K

Abstract

We present a systematic study on the physical properties of EuFe$_{2-x}$Ni$_{x}$As$_{2}$ (0$\leq$\emph{x}$\leq$0.2) by electrical resistivity, magnetic susceptibility and thermopower measurements. The undoped compound EuFe$_{2}$As$_{2}$ undergoes a spin-density-wave (SDW) transition associated with Fe moments at 195 K, followed by antiferromagnetic (AFM) ordering of Eu$^{2+}$ moments at 20 K. Ni doping at the Fe site simultaneously suppresses the SDW transition and AFM ordering of Eu$^{2+}$ moments. For $x\geq$0.06, the magnetic ordering of Eu$^{2+}$ moments evolves from antiferromagnetic to ferromagnetic (FM). The SDW transition is completely suppressed for $x\geq$0.16, however, no superconducting transition was observed down to 2 K. The possible origins of the AFM-to-FM transition and the absence of superconductivity in EuFe$_{2-x}$Ni$_{x}$As$_{2}$ system are discussed.