Uniaxial negative thermal expansion in a weak-itinerant-ferromagnetic phase of CoZr$_{2}$H$_{3.49}$
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arXiv
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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866918147905290240 |
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| author | Watanabe, Yuto Suzuki, Kota Katase, Takayoshi Miura, Akira Yamashita, Aichi Mizuguchi, Yoshikazu |
| author_facet | Watanabe, Yuto Suzuki, Kota Katase, Takayoshi Miura, Akira Yamashita, Aichi Mizuguchi, Yoshikazu |
| contents | We discovered unique uniaxial negative thermal expansion (NTE) behavior for a weak-itinerant-ferromagnetic phase of CoZr$_{2}$H$_{3.49}$. CoZr$_{2}$ is known as a superconductor exhibiting uniaxial NTE along the $c$-axis, which is called anomalous thermal expansion (ATE). Additionally, CoZr$_{2}$ is also known as a well-absorbent of hydrogen, and hydrogen insertion raises weak-itinerant ferromagnetism instead of superconductivity. However, the influence of hydrogen insertion on ATE behavior in this system is still unclear. To investigate it, we performed powder synchrotron X-ray diffraction (SXRD) for CoZr$_{2}$H$_{3.49}$. Through Arrott plots analysis, we determined the Curie temperature ($T_{\mathrm{C}}$) to be 139 K, and the Rhodes-Wohlfarth ratio was estimated to be 3.49, which clearly exceeds 1, suggesting the itinerancy of emerging ferromagnetism. Temperature dependencies of lattice constants $a$ and $c$ were extracted from powder SXRD analyses, and we revealed that lattice constant $c$ exhibited NTE behavior below $T_{\mathrm{C}}$. The uniaxial NTE behavior along the $c$-axis can be understood by sharpening an antibonding Co3$dz^{2}$ partial density of states near the Fermi level, linked to the expansion of a one-dimensional Co-Co chain running parallel to the $c$-axis. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_20765 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Uniaxial negative thermal expansion in a weak-itinerant-ferromagnetic phase of CoZr$_{2}$H$_{3.49}$ Watanabe, Yuto Suzuki, Kota Katase, Takayoshi Miura, Akira Yamashita, Aichi Mizuguchi, Yoshikazu Materials Science Strongly Correlated Electrons Superconductivity We discovered unique uniaxial negative thermal expansion (NTE) behavior for a weak-itinerant-ferromagnetic phase of CoZr$_{2}$H$_{3.49}$. CoZr$_{2}$ is known as a superconductor exhibiting uniaxial NTE along the $c$-axis, which is called anomalous thermal expansion (ATE). Additionally, CoZr$_{2}$ is also known as a well-absorbent of hydrogen, and hydrogen insertion raises weak-itinerant ferromagnetism instead of superconductivity. However, the influence of hydrogen insertion on ATE behavior in this system is still unclear. To investigate it, we performed powder synchrotron X-ray diffraction (SXRD) for CoZr$_{2}$H$_{3.49}$. Through Arrott plots analysis, we determined the Curie temperature ($T_{\mathrm{C}}$) to be 139 K, and the Rhodes-Wohlfarth ratio was estimated to be 3.49, which clearly exceeds 1, suggesting the itinerancy of emerging ferromagnetism. Temperature dependencies of lattice constants $a$ and $c$ were extracted from powder SXRD analyses, and we revealed that lattice constant $c$ exhibited NTE behavior below $T_{\mathrm{C}}$. The uniaxial NTE behavior along the $c$-axis can be understood by sharpening an antibonding Co3$dz^{2}$ partial density of states near the Fermi level, linked to the expansion of a one-dimensional Co-Co chain running parallel to the $c$-axis. |
| title | Uniaxial negative thermal expansion in a weak-itinerant-ferromagnetic phase of CoZr$_{2}$H$_{3.49}$ |
| topic | Materials Science Strongly Correlated Electrons Superconductivity |
| url | https://arxiv.org/abs/2509.20765 |