arXiv subjects

K. H. Chow

Publications and source records attributed to K. H. Chow.

21 records · Page 2Linked to original sources

arXiv2005

Beta-Detected NQR in Zero Field with a Low Energy Beam of \nuc{8}{Li}$^+$

Beta-detected nuclear quadrupole resonances (\bnqr) at zero field are observed using a beam of low energy highly polarized radioactive \nuc{8}{Li}$^+$. The resonances were detected in SrTiO$_3$, Al$_2$O$_3$ and Sr$_2$RuO$_4$ single crystals by monitoring the beta-decay anisotropy as a function of a small audio frequency magnetic field. The resonances show clearly that \nuc{8}{Li} occupies one site with non-cubic symmetry in SrTiO$_3, two in Al$_2$O$_3$ and three sites in Sr$_2$RuO$_4$. The resonance amplitude and width are surprisingly large compared to the values expected from transitions between the $|\pm 2> \leftrightarrow |\pm 1>$ spin states, indicating a significant mixing between the $|\pm m>$ quadrupolar split levels.

cond-mat.str-el↗

arXiv2004

Muonium as a shallow center in GaN

A paramagnetic muonium (Mu) state with an extremely small hyperfine parameter was observed for the first time in single-crystalline GaN below 25 K. It has a highly anisotropic hyperfine structure with axial symmetry along the [0001] direction, suggesting that it is located either at a nitrogen-antibonding or a bond-centered site oriented parallel to the c-axis. Its small ionization energy (=< 14 meV) and small hyperfine parameter (--10^{-4} times the vacuum value) indicate that muonium in one of its possible sites produces a shallow state, raising the possibility that the analogous hydrogen center could be a source of n-type conductivity in as-grown GaN.

cond-mat.mtrl-sci↗

arXiv1996

Muon Spin Relaxation Investigation of the Spin Dynamics of Geometrically Frustrated Antiferromagnets Y2Mo2O7 and Tb2Mo2O7 Static Critical Behavior of the Spin-Freezing

The spin dynamics of geometrically frustrated pyrochlore antiferromagnets Y2Mo2O7 and Tb2Mo2O7 have been investigated using muon spin relaxation. A dramatic slowing down of the moment fluctuations occurs as one approaches the spin freezing temperatures (TF=22 K and 25 K respectively) from above. Below TF there is a disordered magnetic state similar to that found in a spin glass but with a residual muon spin relaxation rate at low temperatures. These results show that there is a large density of states for magnetic excitations in these systems near zero energy.

cond-mat↗