Large saturation moment and high ferromagnetic transition temperature in a structurally disordered inverse Heusler alloy Fe2RuGe

Sudip Chakraborty; Shuvankar Gupta; Vidha Bhasin; Santanu Pakhira; Céline Barreteau; Jean-Claude Crivello; Shambhu Nath Jha; Dibyendu Bhattacharyya; Maxim Avdeev; Valérie Paul-Boncour; Jean-Marc Greneche; Eric Alleno; Chandan Mazumdar

arXiv · 2306.14831

Large saturation moment and high ferromagnetic transition temperature in a structurally disordered inverse Heusler alloy Fe2RuGe

Sudip Chakraborty·Shuvankar Gupta·Vidha Bhasin·Santanu Pakhira·Céline Barreteau·Jean-Claude Crivello·Shambhu Nath Jha·Dibyendu Bhattacharyya·Maxim Avdeev·Valérie Paul-Boncour·Jean-Marc Greneche·Eric Alleno·Chandan Mazumdar

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Abstract

We report the successful synthesis of a new 4$d$ based polycrystalline inverse Heusler alloy Fe$_2$RuGe by an arc melting process and have studied in detail its structural, magnetic and transport properties complemented with first principle calculations. X-ray and neutron diffraction, Extended X-ray Absorption Fine Structure and $^{57}$Fe M\"{o}ssbauer spectroscopic studies confirm the single phase nature of the system where the Fe and Ru atoms are randomly distributed in the 4$c$ and 4$d$ Wyckoff positions in a ratio close to 50:50. The formation of the disordered structure is also confirmed by the theoretical energy minimization calculation. Despite the random cross-site disorder of Fe and Ru atoms, magnetic measurements suggest not only a high Curie temperature of $\sim$860\,K, but also a large saturation magnetic moment $\sim$4.9\,$\mu_B$ per formula unit at 5\,K, considerably exceeding the theoretical limit (4\,$\mu_B$ per formula unit) predicted by the Slater-Pauling rule. Only a few Fe-based inverse Heusler alloys are known to exhibit such high Curie temperatures. Neutron diffraction analysis coupled with the isothermal magnetization value indicates that the magnetic moments in Fe$_2$RuGe are associated with Fe-atoms only, which is also confirmed by M\"ossbauer spectrometry. Interestingly, in comparison to the cubic or hexagonal phase of the parent compound, Fe$_3$Ge, the Curie temperature of Fe$_2$RuGe has increased significantly despite the substitution of the nonmagnetic, yet isoelectronic element Ru in this structurally disordered compound. Our theoretical calculation reveals that the large Fe moment ($\sim2.8\mu_B$/Fe) on the 4$b$ site can be attributed to a charge transfer from this Fe site towards its Ru neighbours. Such a substantial increase in magnetic moment due to electron charge transfer has not previously been reported in a Heusler alloy system.

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Sudip Chakraborty, Shuvankar Gupta, Vidha Bhasin, Santanu Pakhira, Céline Barreteau, Jean-Claude Crivello, Shambhu Nath Jha, Dibyendu Bhattacharyya, Maxim Avdeev, Valérie Paul-Boncour, Jean-Marc Greneche, Eric Alleno, Chandan Mazumdar. 2023-06-26. Large saturation moment and high ferromagnetic transition temperature in a structurally disordered inverse Heusler alloy Fe2RuGe. https://arxiv.org/abs/2306.14831

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