Origin of modulated phases and magnetic hysteresis in TmB_4

We investigate the low temperature magnetic phases in TmB_4, a metallic quantum magnet on the geometrically frustrated Shastry-Sutherland lattice, using co-ordinated experimental and theoretical studies. Our results provide an explanation for the appearance of the intriguing fractional plateau in TmB_4 and accompanying magnetic hysteresis. Together with observation of the bump in the half-plateau, our results support the picture that the magnetization plateau structure in TmB_4 is strongly influenced by the zero-field modulated phases. We present a phenomenological model to explain the appearance of the modulated phases and a microscopic Hamiltonian that captures the complete magnetic behavior of TmB_4.Comment: 7 pages, 5 figure

Hysteretic magnetoresistance and unconventional anomalous Hall effect in the frustrated magnet TmB_4

We study TmB_4, a frustrated magnet on the Archimedean Shastry-Sutherland lattice, through magnetization and transport experiments. The lack of anisotropy in resistivity shows that TmB_4 is an electronically three-dimensional system. The magnetoresistance (MR) is hysteretic at low-temperature even though a corresponding hysteresis in magnetization is absent. The Hall resistivity shows unconventional anomalous Hall effect (AHE) and is linear above saturation despite a large MR. We propose that complex structures at magnetic domain walls may be responsible for the hysteretic MR and may also lead to the AHE

Local lattice instability and stripes in the CuO 2 plane of the La 1.85 Sr 0.15 CuO 4 system by polarized XANES and EXAFS

Temperature-dependent polarized Cu K-edge x-ray absorption has been used to investigate local structural distortions in the ${\mathrm{CuO}}_{2}$ plane of the ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_{4}$ system. The Cu-O pair distribution shows the presence of a minority phase containing ${\mathrm{CuO}}_{6}$ octahedra characterized by a shorter Cu-O(apical) bond (\ensuremath{\Delta}R\ensuremath{\sim}-0.1 \AA{}) and two longer Cu-O(planar) bonds (\ensuremath{\Delta}R\ensuremath{\sim}+0.08 \AA{}) and a tilting angle of 16\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}2\ifmmode^\circ\else\textdegree\fi{}. The temperature-dependent distortions show a maximum around T (\ensuremath{\sim}1.${6\mathrm{T}}_{\mathrm{c}}$) and a minimum at ${\mathrm{T}}_{\mathrm{c}}$ (\ensuremath{\sim}35 K). The data show the coexistence of two types of doped charges in different stripes in the superconducting phase