Mn-doped Crystals Research Articles

Thermoelectric Power of Degenerate Magnetic Semiconductor

The thermoelectric power α has been measured for degenerate magnetic semiconductor Sn 1- x Mn x Te ( x <0.19) with carrier concentration of (1-8) ×10 20 cm -3 over a wide range of temperature 300-4.2 K. The α- T curves of undoped crystals ( x =0) can be explained by the Rogers theoretical expression for α which takes account of intravalley acoustic phonon scattering and two-valence-band model, together with the variation of the band gap and carrier concentration with temperature. In the Mn-doped crystals α has a contribution from ionized impurity scattering. In addition, their α- T curves show a maximum near 20–25 K associated with magnetic ordering. The anomalous thermopowers are compared with the Kasuya theory, with the total angular momentum J =2 and paramagnetic Curie temperature θ'=30–40 K. Also we found a small anomaly around 150 K arising from a displacive phase transition of the host lattice.

Ferroelectric domain stabilization in BaTiO3 by bulk ordering of defects

From an analysis of the ac deconstriction of the hysteresis loop and microscopical observation of moving domain walls, it is concluded, that the ferroelectric domain stabilization in Mn-doped BaTiO3 crystals is due to bulk effects. Esr measurements have revealed that in reduced crystals Mn2+-V0 associates exist, having an excess orientation parallel to Ps-. It is hypothesized that the domain stabilization processes involve a gradual orientation of polar defect associates of this type.

Thermotransport of 85Sr and 54Mn in potassium chloride single crystals

The thermotransport of 85Sr and 54Mn tracers in single crystals of KCl was measured in the temperature range 950–1025 K, by means of Soret effect measurements. The mean value of the impurity heat of transport was −3.18±0.09 eV for Sr in pure or Sr-doped crystals, and was −5.45±0.83 eV for Mn in pure or Mn-doped crystals. There was no significant difference between values from pure and doped crystals for Sr, but for Mn this may not be the case. A discussion of the experimental and theoretical limitations of such measurements as a source of information about the heats of transport for individual jumps was given, and a comparison made with earlier thermotransport measurements in simple ionic solids.

Preferential nucleation of Au on Mn-doped NaCl crystals

Preferential nucleation of Au on Mn-doped NaCl crystals

Electrical resistivity of Mn-doped SnTe crystals at low temperature

The temperature dependence of the resistivity over the range 1.8–20 K has been measured on the narrow-gap semiconductor SnTe with various Mn contents (<2.2at.%) and carrier concentrations [p = (1.2–8) × 1020 cm−3]. The resistivity shows an anomaly at some magnetic ordering temperature T m, which depends sublinearly on the Mn content c, but not linearly. However, together with a negative magnetoresistance, we have confirmed that the carrier scattering in this crystal is due to the s-d interaction as in dilute magnetic alloys.

Cathode ray coloration of Mn-doped CaF2 crystals

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Über die züchtung von grösseren reinen und dotierten ZnO-kristallen aus der gasphase

Large single crystals of ZnO (up to 20 g weight) have been grown by oxidation of Zn-vapour. The crystals contain foreign impurities in a concentration of about 1–3 ppm. Furthermore, there have been grown also Li-, Na-, Cu-, Ga-, In- and Mn-doped crystals using this method.

Excitation and temperature dependence of the blue luminescence of ZnS crystals

The blue luminescence of pure and Al-, Au-, Ag-, Cu-, and Mn-doped ZnS crystals has been studied in the temperature range between LNT and RT and for different wavelengths of the exciting UV-light. All investigated crystals emit two blue bands. The energies of the maxima of these emission bands are independent of the temperature. The temperature dependence of the intensity ratio of the two blue luminescence bands can simulate a temperature shift of the blue emission. The experimental results support the assumption of an essentially uniform structure of the luminescence complex responsible for the visible luminescence of pure and doped ZnS phosphors.

Optical and ESR studies in pure and Mn-doped LiF crystals

Abstract Growth of F absorption band with the time of X-irradiation at RT and the changes caused in the F absorption as a function of F light and thermal bleaching along with the simultaneous ESR studies in pure and Mn-doped LiF single crystals are reported.

Notizen: EPR an Mn-dotiertem KBr

The paramagnetic resonance spectra of Mn-doped single crystals of KBr were studied at 35 GHz. Crystals, heated at 600 °C and dropped into liquid nitrogen, show the spectra of Mn++ with a positive ion vacancy bound in the nearest and next-nearest cation site. The spin Hamiltonian constants, measured at LNT, are: g = 2.001 ± 0.001, |A| = (79 ± 2) G, |D| = (646±13) ·10-4 cm-1 , |E|=(124±3) · 10-4 cm-1 and g = 2.001 ± 0.001, |A| = ( 79 ± 2 ) G , |D|=(918±20) ·10-4cm-1 , |E| = 0 . Two new isotropic sixline spectra are found in such quenched crystals after X-radiating at RT with g = 2.003± 0.001, |A| = ( 20 ± 1 ) G and g=2.002 ± 0.001, |A |=(195±10) G.

Photo-Induced Magnetic-Susceptibility Changes in Mn-Doped ZnS Crystals

The magnetic susceptibilities χ of several Zn1−fMnfS cyrstals (0.004&amp;lt;f&amp;lt;0.4) have been measured (77°−400°K). From the temperature dependence of χ, a large negative Weiss constant is found, consistent with indirect exchange between neighboring Mn atoms. Measurements have also been made with the mixed crystals subjected simultaneously to optical radiation from a 450 W Xenon source. A decrease Δχe not ascribable to heating and attributed to electronic excitation is observed and becomes greater with increasing concentration of the Mn. This effect occurs only for wavelengths below 5400 Å. Multiplicity changes of the Mn, which accompany the optical excitation, are believed to be the main factor to which this photo-induced effect can be attributed. The lifetime of the excited states, as obtained from the decay of the susceptibility change and separately from the magnitude of the change combined with the incident photon flux, is longer than that predicted from the luminescence. We conclude that the Mn atoms responsible for Δχe are not the isolated Mn which contribute to luminescence but are more probably interacting Mn atoms. The analysis of the data is confirmed by a similar study of ZnS:Cr crystals, where an enhancement of paramagnetism is observed, in agreement with spin resonance and optical studies.

Effect of Optical and Thermal Bleaching on the uv Bands in Highly Pure and Mn-Doped KCl Crystals

Effect of Optical and Thermal Bleaching on the uv Bands in Highly Pure and Mn-Doped KCl Crystals