54 research outputs found
B-T phase diagram of CoCr2O4 in magnetic fields up to 14 T
We have measured the magnetization and specific heat of multiferroic CoCr2O4
in magnetic fields up to 14 T. The high-field magnetization measurements
indicate a new phase transition at T* = 5 - 6 K. The phase between T* and the
lock-in transition at 15 K is characterized by magnetic irreversibility. At
higher magnetic fields, the irreversibility increases. Specific-heat
measurements confirm the transition at T*, and also show irreversible behavior.
We construct a field-temperature phase diagram of CoCr2O4.Comment: 4 page
Broadband spectroscopy of astrophysical ice analogues: II. Optical constants of CO and CO ices in the terahertz and infrared ranges
Context: Broadband optical constants of astrophysical ice analogues in the
infrared (IR) and terahertz (THz) ranges are required for modeling the dust
continuum emission and radiative transfer in dense and cold regions, where
thick icy mantles are formed on the surface of dust grains. Aims: In this
paper, the THz time-domain spectroscopy (TDS) and the Fourier-transform IR
spectroscopy (FTIR) are combined to study optical constants of CO and CO
ices in the broad THz-IR spectral range. Methods: The measured ices are grown
at cryogenic temperatures by gas deposition on a cold Si window. A method to
quantify the broadband THz-IR optical constants of ices is developed based on
the direct reconstruction of the complex refractive index of ices in the THz
range from the TDS data, and the use of the Kramers-Kronig relation in the IR
range for the reconstruction from the FTIR data. Uncertainties of the
Kramers-Kronig relation are eliminated by merging the THz and IR spectra. The
reconstructed THz-IR response is then analyzed using classical models of
complex dielectric permittivity. Results: The complex refractive index of CO
and CO ices deposited at the temperature of K is obtained in the range
of 0.3--12.0 THz. Based on the measured dielectric constants, opacities of the
astrophysical dust with CO and CO icy mantles are computed. Conclusions:
The developed method can be used for a model-independent reconstruction of
optical constants of various astrophysical ice analogs in a broad THz-IR range.
Such data can provide important benchmarks to interpret the broadband
observations from the existing and future ground-based facilities and space
telescopes. The reported results will be useful to model sources that show a
drastic molecular freeze-out, such as central regions of prestellar cores and
mid-planes of protoplanetary disks, as well as CO and CO snow lines in
disks.Comment: Accepted for publication in A&A, 9 pages, 7 figure
Sub-wavelength-resolution imaging of biological tissues using THz solid immersion microscopy
We have proposed a method of THz soli
In vitro terahertz spectroscopy of malignant brain gliomas embedded in gelatin slab
In our work, we have performed in vitro terahert
In vitro terahertz spectroscopy of gelatin-embedded human brain tumors - a pilot study
We have performed the in vitro terahertz (THz) spectroscopy of human brain tumors. In order to x tissue
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