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arXiv · 1803.05905

Critical behavior of the van der Waals bonded ferromagnet Fe$_{3-x}$GeTe$_2$

Yu Liu·V. N. Ivanovski·C. Petrovic
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Abstract

The critical properties of the single-crystalline van der Waals bonded ferromagnet Fe$_{3-x}$GeTe$_2$ were investigated by bulk dc magnetization around the paramagnetic (PM) to ferromagnetic (FM) phase transition. The Fe$_{3-x}$GeTe$_2$ single crystals grown by self-flux method with Fe deficiency $x \approx 0.36$ exhibit bulk FM ordering below $T_c = 152$ K. The Mössbauer spectroscopy was used to provide information on defects and local atomic environment in such crystals. Critical exponents $β= 0.372(4)$ with a critical temperature $T_c = 151.25(5)$ K and $γ= 1.265(15)$ with $T_c = 151.17(12)$ K are obtained by the Kouvel-Fisher method whereas $δ= 4.50(1)$ is obtained by a critical isotherm analysis at $T_c = 151$ K. These critical exponents obey the Widom scaling relation $δ= 1+γ/β$, indicating self-consistency of the obtained values. With these critical exponents the isotherm $M(H)$ curves below and above the critical temperatures collapse into two independent universal branches, obeying the single scaling equation $m = f_\pm(h)$, where $m$ and $h$ are renormalized magnetization and field, respectively. The exponents determined in this study are close to those calculated from the results of the renormalization group approach for a heuristic model of three-dimensional Heisenberg ($d = 3, n = 3$) spins coupled with the attractive long-range interactions between spins that decay as $J(r)\approx r^{-(3+σ)}$ with $σ=1.89$.

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Yu Liu, V. N. Ivanovski, C. Petrovic. 2018-03-14. Critical behavior of the van der Waals bonded ferromagnet Fe$_{3-x}$GeTe$_2$. https://doi.org/10.1103/physrevb.96.144429

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