Browsing by Author "Wang, Jiakui K."

Now showing 1 - 5 of 5
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    An itinerant antiferromagnetic metal without magnetic constituents
    (Nature Publishing Group, 2015) Svanidze, E.; Wang, Jiakui K.; Besara, T.; Liu, L.; Huang, Q.; Siegrist, T.; Frandsen, B.; Lynn, J.W.; Nevidomskyy, Andriy H.; Gamża, Monika B.; Aronson, M.C.; Uemura, Y.J.; Morosan, E.
    The origin of magnetism in metals has been traditionally discussed in two diametrically opposite limits: itinerant and local moments. Surprisingly, there are very few known examples of materials that are close to the itinerant limit, and their properties are not universally understood. In the case of the two such examples discovered several decades ago, the itinerant ferromagnets ZrZn2 and Sc3In, the understanding of their magnetic ground states draws on the existence of 3d electrons subject to strong spin fluctuations. Similarly, in Cr, an elemental itinerant antiferromagnet with a spin density wave ground state, its 3d electron character has been deemed crucial to it being magnetic. Here, we report evidence for an itinerant antiferromagnetic metal with no magnetic constituents: TiAu. Antiferromagnetic order occurs below a Néel temperature of 36 K, about an order of magnitude smaller than in Cr, rendering the spin fluctuations in TiAu more important at low temperatures. This itinerant antiferromagnet challenges the currently limited understanding of weak itinerant antiferromagnetism, while providing insights into the effects of spin fluctuations in itinerant–electron systems.
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    Chemical tuning of electrical transport in Ti1−xPtxSe2−y
    (American Physical Society, 2015) Chen, Justin S.; Wang, Jiakui K.; Carr, Scott V.; Vogel, Sven C.; Gourdon, Olivier; Dai, Pengcheng; Morosan, E.
    The structural and transport properties of polycrystalline Ti1−xPtxSe2−y(x≤0.13,y≤0.2) are studied, revealing highly tunable electrical properties, spanning nearly ten orders of magnitude in scaled resistivity. Using x-ray and neutron diffraction, Pt is found to dope on the Ti site. In the absence of Pt doping (for x=0), Se deficiency (y>0) increases the metallic character of TiSe2, while a large increase of the low-temperature resistivity is favored by a lack of Se deficiency (y=0) and increasing amounts of doped Pt (x>0). The chemical tuning of the resistivity in Ti1−xPtxSe2−y with Se deficiency and Pt doping results in a metal-to-insulator transition. Simultaneous Pt doping and Se deficiency (x,y>0) confirms the competition between the two opposing trends in electrical transport, with the main outcome being the suppression of the charge density wave transition below 2 K for y=2x=0.18. Band structure calculations on a subset of Ti1−xPtxSe2−y compositions are in line with the experimental observations.
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    High hardness in the biocompatible intermetallic compound β-Ti3Au
    (AAAS, 2016) Svanidze, Eteri; Besara, Tiglet; Ozaydin, M. Fevsi; Tiwary, Chandra Sekhar; Wang, Jiakui K.; Radhakrishnan, Sruthi; Mani, Sendurai; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Ajayan, Pulickel M.; Morosan, E.
    The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti–Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials.
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    Magnetic and transport properties of the layered transition-metal pnictides R3T4As4O2−δ (R = La, Ce, Pr, Nd, and Sm, T = Ni, Cu)
    (American Physical Society, 2014) Wang, Jiakui K.; Marcinkova, A.; Chen, Chih-Wei; He, Hua; Aronson, Meigan; Morosan, E.
    The magnetic and transport properties of the novel R3T 4As4O2−δ (R = La, Ce, Pr, Nd and Sm, T = Ni and Cu) layered materials were studied using structural and physical properties measurements. Varying the rare-earth ion led to the observation of diverse physical properties including superconductivity for R = La and T = Ni, ferromagnetic or antiferromagnetic order for R = Ce, Pr, and Sm, or spin-glass behavior in Nd3Ni4As4O2−δ. These complex magnetic and electronic properties are discussed in light of the crystalline anisotropy in these layered compounds.
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    Modulated magnetism and anomalous electronic transport in Ce3Cu4As4O2
    (American Physical Society, 2016) Wang, Jiakui K.; Wu, Shan; Qiu, Yiming; Rodriguez-Rivera, Jose A.; Huang, Qingzhen; Broholm, C.; Morosan, E.
    The complex magnetism and transport properties of tetragonal Ce3Cu4As4O2 were examined through neutron scattering and physical property measurements on polycrystalline samples. The lamellar structure consists of alternating layers of CeCu4As4 with a single square Ce lattice and Ce2O2 bilayers. Peaks in the specific heat at the Néel temperature TN=24 K, T2=16 K, and T3=1.9 K indicate three magnetic phase transitions or distinct crossover phenomena. For T