Traditionally, crystal growers have sought to make materials with perfect crystallinity, i.e. with no defects or lattice imperfections. However, real materials always exhibit some degree of imperfection, and in some cases, these imperfections can dramatically alter their properties from the ideal scenario. We discuss the relevance of lattice imperfections in three intermetallic quantum material families, where the presence or absence of defects plays a crucial role in dictating the electronic and magnetic properties. Our goal is to understand the relationship between structure, defects, and function in these materials.
In studying the MSn4 family, PtSn4 stands out as having unique electrical transport features, including a high residual resistivity ratio (RRR), a key metric for quantifying intrinsic defects in metals. Our results indicate that the transport features in PtSn4 is related to an unusually low defect density, as proved using the aid of electronic transport measurements, scanning tunnelling microscopy (STM) and density functional theory (DFT) calculation. Our work demonstrates that the crystal chemistry in PtSn4 exemplifies a structural Goldilocks effect, where the naturally defect-intolerant Pt and Sn layers support high electron mobilities. Secondly, we study the evolution of the magnetic ground state in NdRh2Ge2 as a function of temperature and magnetic field. NdRh2Ge2 shares a strikingly similar magnetic phase diagram with the Gd-based centrosymmetric skyrmion magnet. However, unlike the Heisenberg moments of Gd, Nd has an Ising-like single-ion anisotropy with significantly smaller moments. We map the magnetic phase diagram of NdRh2Ge2, which shows a cascade of metamagnetic transitions, including both commensurate and incommensurate states. Additionally, a broad Hall anomaly is observed, which originates from coexisting magnetic domains. These results underscore the complex relationship between single-ion anisotropy, electronic structure, and magnetic order, as well as the impact of the defects on properties. Lastly, we report the single crystal growth and characterization of Remeika phases Nd3Rh4Ge13 and Nd3Ir4Ge13, where Rh and Ir are isovalent. Through a process of elimination, the crystal structures of the two variants are determined using powder x-ray and single crystal x-ray diffraction. Additionally, we observe an antiferromagnetic ground state and metamagnetic transitions emerging from the ordered states. These systems enabled us to investigate the effect of Ge vacancies, which appear to be strongly coupled to structural distortions resulting in lower symmetry structures, thereby impacting the electronic and magnetic properties. All these examples highlight the importance of studying material properties in the context of their defects or disorder, which can drive their structural, magnetic and electronic behaviours.
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2025-10-27T09:30:002025-10-27T11:30:00Relevance of lattice imperfections in three intermetallic quantum material familiesEvent Information:
Abstract:
Traditionally, crystal growers have sought to make materials with perfect crystallinity, i.e. with no defects or lattice imperfections. However, real materials always exhibit some degree of imperfection, and in some cases, these imperfections can dramatically alter their properties from the ideal scenario. We discuss the relevance of lattice imperfections in three intermetallic quantum material families, where the presence or absence of defects plays a crucial role in dictating the electronic and magnetic properties. Our goal is to understand the relationship between structure, defects, and function in these materials.
In studying the MSn4 family, PtSn4 stands out as having unique electrical transport features, including a high residual resistivity ratio (RRR), a key metric for quantifying intrinsic defects in metals. Our results indicate that the transport features in PtSn4 is related to an unusually low defect density, as proved using the aid of electronic transport measurements, scanning tunnelling microscopy (STM) and density functional theory (DFT) calculation. Our work demonstrates that the crystal chemistry in PtSn4 exemplifies a structural Goldilocks effect, where the naturally defect-intolerant Pt and Sn layers support high electron mobilities. Secondly, we study the evolution of the magnetic ground state in NdRh2Ge2 as a function of temperature and magnetic field. NdRh2Ge2 shares a strikingly similar magnetic phase diagram with the Gd-based centrosymmetric skyrmion magnet. However, unlike the Heisenberg moments of Gd, Nd has an Ising-like single-ion anisotropy with significantly smaller moments. We map the magnetic phase diagram of NdRh2Ge2, which shows a cascade of metamagnetic transitions, including both commensurate and incommensurate states. Additionally, a broad Hall anomaly is observed, which originates from coexisting magnetic domains. These results underscore the complex relationship between single-ion anisotropy, electronic structure, and magnetic order, as well as the impact of the defects on properties. Lastly, we report the single crystal growth and characterization of Remeika phases Nd3Rh4Ge13 and Nd3Ir4Ge13, where Rh and Ir are isovalent. Through a process of elimination, the crystal structures of the two variants are determined using powder x-ray and single crystal x-ray diffraction. Additionally, we observe an antiferromagnetic ground state and metamagnetic transitions emerging from the ordered states. These systems enabled us to investigate the effect of Ge vacancies, which appear to be strongly coupled to structural distortions resulting in lower symmetry structures, thereby impacting the electronic and magnetic properties. All these examples highlight the importance of studying material properties in the context of their defects or disorder, which can drive their structural, magnetic and electronic behaviours.
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