arXiv subjects

J. -S. Lee

Publications and source records attributed to J. -S. Lee.

22 records · Page 2Linked to original sources

arXiv2010

Interface ferromagnetism and orbital reconstruction in BiFeO3- La0.7Sr0.3MnO3 heterostructures

We report the formation of a novel ferromagnetic state in the antiferromagnet BiFeO3 at the interface with La0.7Sr0.3MnO3. Using x-ray magnetic circular dichroism at Mn and Fe L2,3-edges, we discovered that the development of this ferromagnetic spin structure is strongly associated with the onset of a significant exchange bias. Our results demonstrate that the magnetic state is directly related with an electronic orbital reconstruction at the interface, which is supported by the linearly polarized x-ray absorption measurement at oxygen K-edge.

cond-mat.mtrl-sci↗

arXiv2007

Non-resonant and Resonant X-ray Scattering Studies on Multiferroic TbMn2O5

Comprehensive x-ray scattering studies, including resonant scattering at Mn L-edge, Tb L- and M-edges, were performed on single crystals of TbMn2O5. X-ray intensities were observed at a forbidden Bragg position in the ferroelectric phases, in addition to the lattice and the magnetic modulation peaks. Temperature dependences of their intensities and the relation between the modulation wave vectors provide direct evidences of exchange striction induced ferroelectricity. Resonant x-ray scattering results demonstrate the presence of multiple magnetic orders by exhibiting their different temperature dependences. The commensurate-to-incommensurate phase transition around 24 K is attributed to discommensuration through phase slipping of the magnetic orders in spin frustrated geometries. We proposed that the low temperature incommensurate phase consists of the commensurate magnetic domains separated by anti-phase domain walls which reduce spontaneous polarizations abruptly at the transition.

cond-mat.str-el↗

arXiv2006

Stimulated wave of polarization in spin chains

Stimulated wave of polarization, triggered by a flip of a single spin, presents a simple model of quantum amplification. Previously, it has been found that such wave can be excited in a 1D Ising chain with nearest-neighbor interactions, irradiated by a weak resonant transverse field. Here we explore models with more realistic Hamiltonians, in particular, with natural dipole-dipole interactions. Results of simulations for 1D spin chains and rings with up to nine spins are presented.

quant-ph↗

arXiv2006

Intrinsic degree-correlations in static model of scale-free networks

We calculate the mean neighboring degree function $\bar k_{\rm{nn}}(k)$ and the mean clustering function $C(k)$ of vertices with degree $k$ as a function of $k$ in finite scale-free random networks through the static model. While both are independent of $k$ when the degree exponent $γ\geq 3$, they show the crossover behavior for $2 < γ< 3$ from $k$-independent behavior for small $k$ to $k$-dependent behavior for large $k$. The $k$-dependent behavior is analytically derived. Such a behavior arises from the prevention of self-loops and multiple edges between each pair of vertices. The analytic results are confirmed by numerical simulations. We also compare our results with those obtained from a growing network model, finding that they behave differently from each other.

cond-mat.stat-mech↗