1,508 research outputs found
Study of the ground state properties of using SR
is an insulating system where the magnetic Ho ions
have an Ising character, and interact mainly through magnetic dipolar fields.
We used the muon spin relaxation technique to study the nature of the ground
state for samples with x=0.25, 0.12, 0.08, 0.045 and 0.018. In contrast with
some previous works, we have not found any signature of canonical spin glass
behavior down to 15mK. Instead, below 300mK we observed
dynamic magnetism characterized by a single correlation time with a temperature
independent fluctuation rate. We observed that this low temperature fluctuation
rate increases with x up to 0.08, above which it levels off. The 300mK energy
scale corresponds to the Ho3+ hyperfine interaction strength, suggesting that
the hyperfine interaction may be intimately involved with the spin dynamics in
this system
2D Kagome Ordering in the 3D Frustrated Spinel Li2Mn2O4
muSR experiments on the geometrically frustrated spinel oxide, Li2Mn2O4, show
the development of spin correlations over a range of length scales with
decreasing temperature. Increased relaxation below 150 K is consistent with the
onset of spin correlations. Below 50 K, spin order on a length scale, which is
long range for the muSR probe, appears abruptly in temperature, consistent with
prior neutron diffraction results. The oscillations in the zero field asymmetry
are analyzed using a three frequency model. By locating the muon site this is
shown to be consistent with the unexpected 2D q = root 3 x root 3 structure on
the Kagome planes proposed originally from neutron data. Longitudinal field
data demonstrate that some spin dynamics persist even at 2 K. Thus, a very
complex magnetic ground state, featuring the co-existence of long length scale
2D ordering and significant spin dynamics, is proposed. This is unusual
considering the 3D topology of the Mn3+ spins in this material.Comment: 9 pages, 9 figures, to be submitted to J. Phys. Cond. Mat
Muon Spin Relaxation Studies of Magnetic-Field-Induced Effects in High- Superconductors
Muon spin relaxation (SR) measurements in high transverse magnetic
fields () revealed strong field-induced quasi-static
magnetism in the underdoped and Eu doped (La,Sr)CuO and
LaBaCuO, existing well above and . The
susceptibility-counterpart of Cu spin polarization, derived from the muon spin
relaxation rate, exhibits a divergent behavior towards K. No
field-induced magnetism was detected in overdoped
LaSrCuO, optimally doped Bi2212, and Zn-doped
YBaCuO.Comment: 4 pages, 4 color figure
Surface collective modes in the topological insulators BiSe and BiSbTeSe
We used low-energy, momentum-resolved inelastic electron scattering to study
surface collective modes of the three-dimensional topological insulators
BiSe and BiSbTeSe. Our goal was to
identify the "spin plasmon" predicted by Raghu and co-workers [S. Raghu, et
al., Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary
collective mode is a surface plasmon arising from the bulk, free carrers in
these materials. This excitation dominates the spectral weight in the bosonic
function of the surface, , at THz energy scales, and
is the most likely origin of a quasiparticle dispersion kink observed in
previous photoemission experiments. Our study suggests that the spin plasmon
may mix with this other surface mode, calling for a more nuanced understanding
of optical experiments in which the spin plasmon is reported to play a role.Comment: 5 pages, 4 figure
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