# Magnetic order of intermetallic FeGa$_{3-y}$Ge$_y$ studied by $\mu$SR and $^{57}$Fe M\"ossbauer spectroscopy

## TL;DR

This study investigates the magnetic properties of FeGa$_{3-y}$Ge$_{y}$ crystals using $bc$SR and M"ossbauer spectroscopy, revealing a transition from short-range to long-range ferromagnetic order with doping.

## Contribution

It provides detailed insights into how Ge doping influences magnetic order and spin fluctuations in FeGa$_{3-y}$Ge$_{y}$, highlighting the role of local atomic environment.

## Key findings

- Weak ferromagnetism appears at higher doping levels.
- Transition from short-range to long-range magnetic order with doping.
- Internal magnetic fields are oriented perpendicular to the c-axis.

## Abstract

Temperature dependent magnetization, muon spin rotation and $^{57}$Fe M\"ossbauer spectroscopy experiments performed on crystals of intermetallic FeGa$_{3-y}$Ge$_{y}$ ($y=0.11,0.14,0.17,0.22,0.27$, $0.29,0.32$) are reported. Whereas at $y=0.11$ even a sensitive magnetic microprobe such as $\mu$SR does not detect magnetism, all other samples display weak ferromagnetism with a magnetic moment of up to 0.22 $\mu_B$ per Fe atom. As a function of doping and of temperature a crossover from short range to long range magnetic order is observed, characterized by a broadly distributed spontaneous internal field. However, the $y=0.14$ and $y=0.17$ remain in the short range ordered state down to the lowest investigated temperature. The transition from short range to long range order appears to be accompanied by a change of the character of the spin fluctuations, which exhibit spin wave excitations signature in the LRO part of the phase diagram. M\"ossbauer spectroscopy for $y=0.27$ and 0.32 indicates that the internal field lies in the plane perpendicular to the crystallographic $c$ axis. The field distribution and its evolution with doping suggest that the details of the Fe magnetic moment formation and the consequent magnetic state are determined not only by the dopant concentration but also by the way the replacement of the Ga atoms surrounding the Fe is accomplished.