Anomalous Transport Properties of n-CdCr₂Se₄ Single Crystals Near the Curie Temperature

Anomalous increases of the thermoelectric power (the Seebeck coefficient α) and the thermal conductivity k in n- type CdCr₂Se₄ single crystals are found near the Curie temperature Tc. The temperature dependences of the magnetic moment μB and the dipolar spin-spin relaxation time τₛ near Tc suggest that these effects can be attributed to a magnon drag

Physical Properties of Magnetic Domain Switching in a Single Crystal of an Anti-Ferro Magnetic Medium Cr₂O₃

The physical properties of a domain switching under an application of electric and magnetic fields are described, with respect to a single crystal of Cr₂O₃ which belongs in a magnetic point group 3 m. Major results obtained in this study are as follows : (1) experimental results on anisotropic tensor components of a magnetic susceptibility in the C_2O₃ single crystal are found to be in reasonable agreement with the theoretical result in the case of 3m, in which the non-diagonal elements xᵢj are zero and X₁₁＝X₂₂ is required. (2) A temperature dependence of a domain switching time τₛ of the used Cr₂O₃ single crystal follows to approximately 1.6×10¹⁷ exp (―9550/T). From the numerical value in the parenthesis, it appears that the used crystal has an average energy of domain walls corresponding to 0.86 eV. Further, it is concluded that an inversion probability in the domain switching in general depends on the Boltzmann factor

Negative Resistance in Semiconductors (InSb)

We extend the theory of double injection in insulators, derived by Lampert, so as to adapt it to the case of extrinsic semiconductors. This new treatment is shown to agree reasonably well with our experimentally observed features for n⁺p-InSb diodes at low temperature (77°K). Three outstanding features are revealed by the present analysis : (1) The relation of Vᴍ=(1/β)·VᴛH pointed out by Lampert is available only in the case that the recombination density NR is much larger than the free carrier density P₀ (or N₀), i.e., NR>l0⁵·P₀, where Vᴍ and VᴛH are the minimum and maximum voltages respectively, β is the capture rate for electrons and holes. (2) The greater the capture rate β is, the greater the region of the negative resistance becomes. In semiconductors, however, the magnitude of the region is vigorously depedent on a modified recombination density R=NR/P₀ (or NR/N₀). (3) The value of the mobility ratio b=μₙ/μₚ is concerned with a rise in the semicoductor region, and the relation of J∝V² is satisfactory, if b<lO. In the material with high mobility as a case of InSb, however, the current rises steeply in proportion to the several powers of the voltage, e.g. J∝ V⁴, when b=50. As above mentioned, we can sufficiently explain the behavior of double injection in semiconductors or insulators by this treatment