Zhiling Dun

Static and dynamical properties of the spin-1/2 equilateral triangular-lattice antiferromagnet Ba3CoSb2O9

We present single-crystal neutron scattering measurements of the spin-1/2 equilateral triangular-lattice antiferromagnet Ba_{3}CoSb_{2}O_{9}. Besides confirming that the Co^{2+} magnetic moments lie in the ab plane for zero magnetic field and then determining all the exchange parameters of the minimal quasi-2D spin Hamiltonian, we provide conclusive experimental evidence of magnon decay through observation of intrinsic line broadening. Through detailed comparisons with the linear and nonlinear spin-wave theories, we also point out that the large-S approximation, which is conventionally employed to predict magnon decay in noncollinear magnets, is inadequate to explain our experimental observation. Thus, our results call for a new theoretical framework for describing excitation spectra in low-dimensional frustrated magnets under strong quantum effects.

Excess-hole induced high temperature polarized state and its correlation with the multiferroicity in single crystalline DyMnO3

Controlling the ferroelectricity and magnetism in multiferroic materials has been an important research topic. We report the formation of a highly polarized state in multiferroic DyMnO3 single crystals which develops well above the magnetic transition temperatures, and we attribute it the thermally stimulated depolarization current effect of excess holes forming Mn4+ ions in the system. We also show that this high temperature polarized state intimately correlates with the lower temperature ferroelectric state that is induced by the incommensurate spiral magnetic order of Mn spins. This study demonstrate an efficient approach to tune the multiferroicity in the manganite system.

Tuning the ferroelectric state in multiferroic TbMnO3 single crystal by a trapped-charge-induced internal electric field

The pyroelectric current effects in multiferroic TbMnO3 single crystal are reinvestigated in a wide temperature range. We report a pyroelectric current peak occurring around T = 107 K, which is much higher than the magnetic phase transition temperatures, after poling the sample from T ≥ 60 K to low temperatures, and we attribute it to the thermal release of trapped-charges in TbMnO3. We also show that the trapped-charges form a strong internal electric field that remarkably controls the ferroelectric polarization state induced by the cycloidal Mn3+ spins at lower temperature.

Strong competition between orbital ordering and itinerancy in a frustrated spinel vanadate

In this study, the crossover from localized to itinerant electron regimes in the geometrically frustrated spinel system Mn1-xCoxV2O4 is explored by neutron-scattering measurements, first-principles calculations, and spin models. At low Co doping, the orbital ordering (OO) of the localized V3+ spins suppresses magnetic frustration by triggering a tetragonal distortion. At high Co doping levels, however, electronic itinerancy melts the OO and lessens the structural and magnetic anisotropies, thus increasing the amount of geometric frustration for the V-site pyrochlore lattice. Contrary to the predicted paramagentism induced by chemical pressure, the measured noncollinear spin states in the Co-rich region of the phase diagram provide a unique platform where localized spins and electronic itinerancy compete in a geometrically frustrated spinel.

Structural and magnetic phase transitions in EuTi1-xNbxO3

Here, we investigate the structural and magnetic phase transitions in EuTi1-xNbxO3 (0≤x≤0.3) with synchrotron powder x-ray diffraction, resonant ultrasound spectroscopy, and magnetization measurements. Upon Nb doping, the Pm

Landau-level spectroscopy of massive Dirac fermions in single-crystalline ZrTe 5 thin flakes

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Evolution of the magnetic and structural properties of Fe

m ↔ I4/mcm structural transition shifts to higher temperatures and the room temperature lattice parameter increases while the magnitude of the octahedral tilting decreases. In addition, Nb substitution for Ti destabilizes the antiferromagnetic ground state of the parent compound and long-range ferromagnetic order is observed in the samples with x≥0.1. Moreover, the structural transition in pure and doped compounds is marked by a dramatic step-like softening of the elastic moduli near TS, which resembles that of SrTiO3 and can be adequately modeled using the Landau free energy model employing the same coupling between strain and octahedral tilting order parameter as previously used to model SrTiO3.

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We present a systematic study of the structural and magnetic properties of two branches of the rare earth Tripod Kagome Lattice (TKL) family A