1,093 research outputs found
Magnetic properties of Sn/1-x/Cr/x/Te diluted magnetic semiconductors
We present the studies of Sn/1-x/Cr/x/Te semimagnetic semiconductors with
chemical composition x ranging from 0.004 to 0.012. The structural
characterization indicates that even at low average Cr-content x < ?0.012, the
aggregation into micrometer size clusters appears in our samples. The magnetic
properties are affected by the presence of clusters. In all our samples we
observe the transition into the ordered state at temperatures between 130 and
140 K. The analysis of both static and dynamic magnetic susceptibility data
indicates that the spin-glass-like state is observed in our samples. The
addition of Cr to the alloy seems to shift the spin-glass-like transition from
130 K for x = 0.004 to 140 K for x = 0.012.Comment: 4 pages, 4 figure
Methods in Historical Ecology: A Case Study of Tintic Valley, Utah
Through use of repeat photography, archival research, and field observation to reconstruct landscape vegetation patterns and changes across a 120 year period in the upper Tintic Valley of central Utah, researchers found significant changes in landscape vegetation pattern over time, including change in pinyon-juniper woodland area. Previously reported massive woodland harvest associated with early mining, domestic and agricultural activities elsewhere in the Intermountain West also took place in Utah. The impact on woodland area of the agricultural bull fence alone was significant. More recent study area woodland expansion also occurred. Because intensive industrial activity associated with development of the Tintic Mining District occurred prior to the taking of the study\u27s 1911 photographs, those photos failed to reflect presettlement, or even early settlement, vegetation conditions. Overall, results suggest that historical ecological studies must employ a range of overlapping methodologies to accurately interpret the nature and direction of landscape vegetation change. Such information is useful for managing regional ecosystems now and into the future
The magnetic interactions in spin-glasslike Ge/1-x-y/Sn/x/Mn/y/Te diluted magnetic semiconductor
We investigated the nature of the magnetic phase transition in the
Ge/1-x-y/Sn/x/Mn/y/Te mixed crystals with chemical composition changing in the
range of 0.083 < x < 0.142 and 0.012 < y < 0.119. The DC magnetization
measurements performed in the magnetic field up to 90 kOe and temperature range
2-200 K showed that the magnetic ordering at temperatures below T = 50 K
exhibits features characteristic for both spin-glass and ferromagnetic phases.
The modified Sherrington - Southern model was applied to explain the observed
transition temperatures. The calculations showed that the spin-glass state is
preferred in the range of the experimental carrier concentrations and Mn
content. The value of the Mn hole exchange integral was estimated to be J/pd/ =
0.45+/-0.05 eV. The experimental magnetization vs temperature curves were
reproduced satisfactory using the non-interacting spin-wave theory with the
exchange constant J/pd/ values consistent with those calculated using modified
Sherrington - Southern model. The magnetization vs magnetic field curves showed
nonsaturating behavior at magnetic fields B < 90 kOe indicating the presence of
strong magnetic frustration in the system. The experimental results were
reproduced theoretically with good accuracy using the molecular field
approximation-based model of a disordered ferromagnet with long-range RKKY
interaction.Comment: 9 pages, 6 figure
Magnetoresistance of a semiconducting magnetic wire with domain wall
We investigate theoretically the influence of the spin-orbit interaction of
Rashba type on the magnetoresistance of a semiconducting ferromagnetic
nanostructure with a laterally constrained domain wall. The domain wall is
assumed sharp (on the scale of the Fermi wave length of the charge carriers).
It is shown that the magnetoresistance in such a case can be considerably
large, which is in a qualitative agreement with recent experimental
observations. It is also shown that spin-orbit interaction may result in an
increase of the magnetoresistance. The role of localization corrections is also
briefly discussed.Comment: 5 pages, 2 figure
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