6,755 research outputs found
The phase transition in the localized ferromagnet EuO probed by muSR
We report results of muon spin rotation measurements performed on the
ferromagnetic semiconductor EuO, which is one of the best approximations to a
localized ferromagnet. We argue that implanted muons are sensitive to the
internal field primarily through a combination of hyperfine and Lorentz fields.
The temperature dependences of the internal field and the relaxation rate have
been measured and are compared with previous theoretical predictions.Comment: 4 pages, 4 figure
Thermodynamic and magnetic properties of the layered triangular magnet NaNiO2
We report muon-spin rotation, heat capacity, magnetization, and ac magnetic
susceptibility measurements of the layered spin-1/2 antiferromagnet NaNiO2.
These show the onset of long-range magnetic order below T_N = 19.5K. Rapid muon
depolarization persisting to about 5K above T_N is consistent with the presence
of short-range magnetic order. The temperature and frequency dependence of the
ac susceptibility suggests that magnetic clusters persist above 25K in the
paramagnetic state and that their volume fraction decreases with increasing
temperature. A frequency dependent peak in the ac magnetic susceptibility at
T_sf = 3K is observed, consistent with a slowing of spin fluctuations at this
temperature. A partial magnetic phase diagram is deduced.Comment: 4 pages, 4 figure
Determination of characteristic muon precession and relaxation signals in FeAs and FeAs2, possible impurity phases in pnictide superconductors
We report muon-spin relaxation measurements of highly homogeneous samples of
FeAs and FeAs2, both previously found as impurity phases in some samples of
recently synthesized pnictide superconductors. We observe well defined muon
precession in the FeAs sample with two precession frequencies of 38.2(3) and
22.7(9) MHz at 7.5 K, with the majority of the amplitude corresponding to the
lower frequency component. In FeAs2 we confirm previous measurements showing
that no long-ranged magnetic order occurs above 2 K and measure the muon spin
relaxation rate, which increases on cooling. Our results exclude the
possibility that previous muon-spin relaxation measurements of pnictide
superconductors have been measuring the effect of these possible impurities.Comment: 4 pages, 3 figures, corrected Figure
Magnetic order in the quasi-one-dimensional spin 1/2 chain, copper pyrazine dinitrate
We present the first evidence of magnetic order in the quasi-one-dimensional
spin 1/2 molecular chain compound, copper pyrazine dinitrate Cu(C4H4N2)(NO3)2}.
Zero field muon-spin relaxation measurements made at dilution refrigerator
temperatures show oscillations in the measured asymmetry, characteristic of a
quasistatic magnetic field at the muon sites. Our measurements provide
convincing evidence for long range magnetic order below a temperature
T_N=107(1) mK. This leads to an estimate of the interchain coupling constant of
|J'|/k_B=0.046 K and to a ratio |J'/J| = 4.4 x 10^-3.Comment: 4 pages, 3 figures. Submitted to Physical Review Letter
Spin freezing and dynamics in Ca_{3}Co_{2-x}Mn_{x}O_{6} (x ~ 0.95) investigated with implanted muons: disorder in the anisotropic next-nearest neighbor Ising model
We present a muon-spin relaxation investigation of the Ising chain magnet
Ca_{3}Co_{2-x}Mn_{x}O_{6} (x~0.95). We find dynamic spin fluctuations
persisting down to the lowest measured temperature of 1.6 K. The previously
observed transition at around T ~18 K is interpreted as a subtle change in
dynamics for a minority of the spins coupling to the muon that we interpret as
spins locking into clusters. The dynamics of this fraction of spins freeze
below a temperature T_{SF}~8 K, while a majority of spins continue to
fluctuate. An explanation of the low temperature behavior is suggested in terms
of the predictions of the anisotropic next-nearest-neighbor Ising model.Comment: 4 pages, 2 figure
Muon-spin relaxation and heat capacity measurements on the magnetoelectric and multiferroic pyroxenes LiFeSi2O6 and NaFeSi2O6
The results of muon-spin relaxation and heat capacity measurements on two
pyroxene compounds LiFeSi2O6 and NaFeSi2O6 demonstrate that despite their
underlying structural similarity the magnetic ordering is considerably
different. In LiFeSi2O6 a single muon precession frequency is observed below
TN, consistent with a single peak at TN in the heat capacity and a commensurate
magnetic structure. In applied magnetic fields the heat capacity peak splits in
two. In contrast, for natural NaFeSi2O6, where multiferroicity has been
observed in zero-magnetic-field, a rapid Gaussian depolarization is observed
showing that the magnetic structure is more complex. Synthetic NaFeSi2O6 shows
a single muon precession frequency but with a far larger damping rate than in
the lithium compound. Heat capacity measurements reproduce the phase diagrams
previously derived from other techniques and demonstrate that the magnetic
entropy is mostly associated with the build up of correlations in the
quasi-one-dimensional Fe3+ chains
Anomalous temperature evolution of the internal magnetic field distribution in the charge-ordered triangular antiferromagnet AgNiO2
Zero-field muon-spin relaxation measurements of the frustrated triangular
quantum magnet AgNiO2 are consistent with a model of charge disproportionation
that has been advanced to explain the structural and magnetic properties of
this compound. Below an ordering temperature of T_N=19.9(2) K we observe six
distinct muon precession frequencies, due to the magnetic order, which can be
accounted for with a model describing the probable muon sites. The precession
frequencies show an unusual temperature evolution which is suggestive of the
separate evolution of two opposing magnetic sublattices.Comment: 4 pages, 3 figure
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