Spin dynamics of FeGa_3−xGe_xstudied by electron spin resonance

Abstract

The intermetallic semiconductor FeGa<sub>3</sub> acquires itinerant ferromagnetism upon electron doping by a partial replacement of Ga with Ge. We studied the electron spin resonance (ESR) of high-quality single crystals of FeGa<sub>3-x</sub>Ge<sub>x</sub> for x from 0 up to 0.162 where ferromagnetic order is observed. For x = 0 we observed a well-defined ESR signal, indicating the presence of pre-formed magnetic moments in the semiconducting phase. Upon Ge doping the occurrence of itinerant magnetism clearly affects the ESR properties below ≈ 40 K whereas at higher temperatures an ESR signal as seen in FeGa<sub>3</sub> prevails independent on the Ge-content. The present results show that the ESR of FeGa<sub>3-x</sub>Ge<sub>x</sub> is an appropriate and direct tool to investigate the evolution of 3d-based itinerant magnetism.

Single Crystal Growth of FeGa3 and FeGa3−xGex from High‐Temperature Solution Using the Czochralski Method

“…Based on the crystal growth results presented here, first measurements of physical properties of binary FeGa 3 and FeGa 3− x Ge x have already been published without mentioning details of the single crystal growth approach . It is outside the scope of the present paper to repeat the results of the physical studies here.…”

“…Starting from a semiconductor, with increased Ge doping the compound performs a crossover to a strongly correlated metal at x = 0.06. [11,18] Arising from the sensitivity of strongly correlated materials to chemical doping, it was found that at the critical Ge concentration of around x = 0.15, the phase shows quantum critical fluctuations and a phase transition from antiferromagnetic to itinerant ferromagnetism at low temperatures. While antiferromagnetic quantum critical systems have already been studied in 4f-and 3d-systems, ferromagnetic quantum criticality is of significant interest for basic research.…”

“…Improvements of the thermopower of FeGa 3 by Ge electron doping revealed important new properties of FeGa 3− x Ge x . Starting from a semiconductor, with increased Ge doping the compound performs a crossover to a strongly correlated metal at x = 0.06 . Arising from the sensitivity of strongly correlated materials to chemical doping, it was found that at the critical Ge concentration of around x = 0.15, the phase shows quantum critical fluctuations and a phase transition from antiferromagnetic to itinerant ferromagnetism at low temperatures.…”

Thermoelectricity in correlated narrow-gap semiconductors

“…Dotted lines for FeAs2 and FeGa3 are activation-law fit extrapolations. CrSb2 is antiferromagnetic below 273K; a complex magnetic order has also been suggested for FeGa3 [36,94].…”

“…• FeSi 1−x Ge x : ferromagnetic metal above x = 3 The onset of a peculiar antiferromagnetic order in CrSb 2 below 273K [65,95] has no visible signature in the susceptibility. 4 with the exception of CrSb 2 below its Néel temperature T N = 273K, and possibly FeGa 3 [36,94].…”