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Tang, Y. S.

Publications and source records attributed to Tang, Y. S..

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Magnetic structure and magnetoelectric coupling in the antiferromagnet Co 5⁢ (Te⁢O 3 ) 4 ⁢Cl 2

The van der Waals (vdW) layered multiferroics, which host simultaneous ferroelectric and magnetic orders, have attracted attention not only for their potentials to be utilized in nanoelectric devices and spintronics, but also offer alternative opportunities for emergent physical phenomena. To date, the vdW layered multiferroic materials are still very rare. In this work, we have investigated the magnetic structure and magnetoelectric (ME) effects in Co 5 ⁢(Te⁢O 3 ) 4 ⁢Cl 2 , a promising multiferroic compound with antiferromagnetic (AFM) Néel point T N ~18 K. The neutron-powder diffraction reveals the noncoplanar AFM state with preferred Néel vector along the c axis, while a spin reorientation occurring between 8 and 15 K is identified, which results from the distinct temperature dependence of the nonequivalent Co site's moment in Co 5 ⁢(Te⁢O 3 ) 4 ⁢Cl 2 . Moreover, it is found that Co 5 ⁢(Te⁢O 3 ) 4 ⁢Cl 2 is one of the best vdW multiferroics studied so far in terms of the multiferroic performance. The measured linear ME coefficient exhibits the emergent oscillation dependence of the angle between magnetic field and electric field, and the maximal value is as big as 45 ps/m. Finally, it is suggested that Co 5 ⁢(Te⁢O 3 ) 4 ⁢Cl 2 is an appreciated platform for exploring the emergent multiferroicity in vdW layered compounds.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Magnetic structure and multiferroicity of Sc-substituted hexagonal YbFeO 3

The hexagonal rare-earth ferrite RFeO 3 family represents a unique class of multiferroics exhibiting weak ferromagnetism, and a strong coupling between magnetism and structural trimerization is predicted. However, the hexagonal structure for RFeO 3 remains metastable in conventional conditions. We have succeeded in stabilizing the hexagonal structure of polycrystalline YbFeO 3 by partial Sc substitution of Yb. Using bulk magnetometry and neutron diffraction, we find that Yb 0.42 Sc 0.58 FeO 3 orders into a canted antiferromagnetic state with the Néel temperature T N ~ 165K, below which the Fe 3+ moments form the triangular configuration in the ab plane and their in-plane projections are parallel to the [100] axis, consistent with magnetic space group P6 3 c'm'. It is determined that the spin canting is aligned along the c axis, giving rise to the weak ferromagnetism. Furthermore, the Fe 3+ moments reorient toward a new direction below reorientation temperature T R ~ 40K, satisfying magnetic subgroup P6 3 , while the Yb 3+ moments order independently and ferrimagnetically along the c axis at the characteristic temperature T Yb ~ 15K. Interestingly, reproducible modulation of electric polarization induced by magnetic field at low temperature is achieved, suggesting that the delicate structural distortion associated with two-up/one-down buckling of the Yb/Sc planes and tilting of the FeO 5 bipyramids may mediate the coupling between ferroelectric and magnetic orders under magnetic field. Furthermore, the present work represents substantial progress to search for high-temperature multiferroics in hexagonal ferrites and related materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1971

After heat distribution of a mobile nuclear power plant

A computer program was developed to analyze the transient afterheat temperature and pressure response of a mobile gas-cooled reactor power plant following impact. The program considers (in addition to the standard modes of heat transfer) fission product decay and transport, metal-water reactions, core and shield melting and displacement, and pressure and containment vessel stress response. Analyses were performed for eight cases (both deformed and undeformed models) to verify operability of the program options. The results indicated that for a 350 psi (241 n/sq cm) initial internal pressure, the containment vessel can survive over 100,000 seconds following impact before creep rupture occurs. Recommendations were developed as to directions for redesign to extend containment vessel life.

Parker, W. G.↗