Absence of Long-Range Order and Magnetic Anisotropy in the Triangular Magnet NdMgAl$_{11}$O$_{19}$
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| Formato: | Preprint |
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2025
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| author | Kumar, Sonu Bastien, Gaël Prokleška, Jan Kempiński, Mateusz Kempiński, Wojciech Załęski, Karol Kancko, Andrej Corrêa, Cinthia Antunes Treu, Tim Gegenwart, Philipp Śliwińska-Bartkowiak, Małgorzata Colman, Ross H. |
| author_facet | Kumar, Sonu Bastien, Gaël Prokleška, Jan Kempiński, Mateusz Kempiński, Wojciech Załęski, Karol Kancko, Andrej Corrêa, Cinthia Antunes Treu, Tim Gegenwart, Philipp Śliwińska-Bartkowiak, Małgorzata Colman, Ross H. |
| contents | We investigated the rare-earth triangular-lattice antiferromagnet NdMgAl$_{11}$O$_{19}$ using single-crystal magnetization (1.8~K $\leq T \leq$ 300~K, $μ_0 H \leq 7$~T) and specific-heat measurements down to 45~mK. The dc susceptibility confirms a well-isolated Kramers doublet ground state with pronounced Ising-type anisotropy, with $g_c \approx 3.7$ and $g_{ab} \approx 1.45$. Curie--Weiss fits yield weak, anisotropic antiferromagnetic exchange, with $θ_c = -0.54$~K and $θ_{ab} = -0.87$~K. Heat-capacity measurements show no long-range magnetic order down to 40~mK, corresponding to a frustration index $f \gtrsim 20$. Instead, $C_m/T$ exhibits a broad maximum near 0.081~K whose magnitude and field evolution are consistent with short-range correlations in an anisotropic triangular lattice. Applied magnetic fields open a Zeeman gap where the specific-heat anomaly follows $Δ= g μ_B μ_0 H$, and $M(H,T)$ is well described by a Brillouin function for an effective $J = 1/2$ moment. The field tuning of the low-temperature entropy manifold allows self-cooling from 1.8~K to 53~mK by adiabatic demagnetisation from a 9~T field. These results identify NdMgAl$_{11}$O$_{19}$ as a nearly ideal weak-exchange triangular magnet with a field-tunable correlated ground state, where two-dimensional crossover effects may emerge from frustrated XXZ interactions. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2505_18898 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Absence of Long-Range Order and Magnetic Anisotropy in the Triangular Magnet NdMgAl$_{11}$O$_{19}$ Kumar, Sonu Bastien, Gaël Prokleška, Jan Kempiński, Mateusz Kempiński, Wojciech Załęski, Karol Kancko, Andrej Corrêa, Cinthia Antunes Treu, Tim Gegenwart, Philipp Śliwińska-Bartkowiak, Małgorzata Colman, Ross H. Strongly Correlated Electrons Materials Science We investigated the rare-earth triangular-lattice antiferromagnet NdMgAl$_{11}$O$_{19}$ using single-crystal magnetization (1.8~K $\leq T \leq$ 300~K, $μ_0 H \leq 7$~T) and specific-heat measurements down to 45~mK. The dc susceptibility confirms a well-isolated Kramers doublet ground state with pronounced Ising-type anisotropy, with $g_c \approx 3.7$ and $g_{ab} \approx 1.45$. Curie--Weiss fits yield weak, anisotropic antiferromagnetic exchange, with $θ_c = -0.54$~K and $θ_{ab} = -0.87$~K. Heat-capacity measurements show no long-range magnetic order down to 40~mK, corresponding to a frustration index $f \gtrsim 20$. Instead, $C_m/T$ exhibits a broad maximum near 0.081~K whose magnitude and field evolution are consistent with short-range correlations in an anisotropic triangular lattice. Applied magnetic fields open a Zeeman gap where the specific-heat anomaly follows $Δ= g μ_B μ_0 H$, and $M(H,T)$ is well described by a Brillouin function for an effective $J = 1/2$ moment. The field tuning of the low-temperature entropy manifold allows self-cooling from 1.8~K to 53~mK by adiabatic demagnetisation from a 9~T field. These results identify NdMgAl$_{11}$O$_{19}$ as a nearly ideal weak-exchange triangular magnet with a field-tunable correlated ground state, where two-dimensional crossover effects may emerge from frustrated XXZ interactions. |
| title | Absence of Long-Range Order and Magnetic Anisotropy in the Triangular Magnet NdMgAl$_{11}$O$_{19}$ |
| topic | Strongly Correlated Electrons Materials Science |
| url | https://arxiv.org/abs/2505.18898 |