Critical behavior in the van derWaals itinerant ferromagnet Fe4GeTe2

The critical phenomenon of the magnetic phase transition in the van derWaals itinerant ferromagnet Fe4GeTe2 has been investigated by measuring the dc magnetization. The compound undergoes a continuous paramagnetic to ferromagnetic phase transition at the Curie temperature T-C = 270.0K. A detailed analysis of magnetization isotherms measured in the vicinity of T-C with magnetic field H applied parallel to the ab plane yields the asymptotic critical exponents beta = 0.37, gamma = 1.20, and delta = 4.21, whereas the magnetization isotherms for H parallel to c yield beta = 0.34, gamma = 1.20, and delta = 4.52. Both sets of the critical exponents obey the scaling relation and scaling equation of the magnetic state predicted by the scaling theory. The renormalization group theory analysis for the critical exponents and the analysis based on the self-consistent renormalization theory of spin fluctuations manifest a quasi-two-dimensional itinerant magnetism in the Fe4GeTe2 single crystal where the magnetic exchange coupling J(r) is the long-range type that decreases spatially slower than r(-4.76). Moreover, a small reduction in the value of beta for H parallel to c attests to the observed weak effective uniaxial magnetic anisotropy of Fe4GeTe2.

Automated summary

The critical phenomenon of magnetic phase transition in the van der Waals itinerant ferromagnet Fe4GeTe2 was investigated, revealing specific critical exponents during the continuous paramagnetic to ferromagnetic transition. The analysis suggests a quasi-two-dimensional itinerant magnetism in Fe4GeTe2 single crystal, with a certain magnetic anisotropy present.