Anisotropy resistivity

Physical Properties Electrical. Electrical properties have been the main focus of study of organic semiconductors, and conductivity studies on organic materials have led to the development of materials with extremely low resistivities and large anisotropies. A discussion of conductivity behaviors for various classes of compounds follows. 

Iron—Aluminum and Iron—Aluminum—Silicon Alloys. The influence of aluminum on the physical and magnetic properties of iron is similar to that of silicon, ie, stabilization of the bcc phase, increased resistivity, decreased ductility, and decreased saturation magnetization, magnetocrystalline anisotropy, and magnetostriction. Whereas Si—Ee alloys are well estabHshed for electrical appHcations, the aluminum—iron alloys have not been studied commercially. However, small (up to ca 0.3%) amounts of A1 have been added to the nonoriented grades of siHcon steel, because the decrease in ductiHty is less with A1 than with Si. 

Radiation Effects. Alpha sihcon carbide exhibits a small degree of anisotropy in radiation-induced expansions along the optical axis and perpendicular to it (58). When diodes of sihcon carbide were compared with sihcon diodes in exposure to kradiation with fast neutrons (59), an increase in forward resistance was noted only at a flux about 10 times that at which the increase occurs in a sihcon diode. In general, it appears that sihcon carbide, having the more tightly bound lattice, is less damaged by radiation than sihcon. 

The specific resistance of natural graphite crystals is ca Hem (room temperature) along the a axis parallel to the network basal plane. The resistance along the c axis (perpendicular to the basal plane) is ca 1 Q. The cja axis anisotropy ratio is, therefore, ca 10 . Screw dislocations within the crystal may short-circuit the current path parallel to the c axis and cause lower anisotropic ratios separation of planes may cause higher anisotropic ratios. 

Here p and pj are the transverse and longitudinal resistivities with respect to the magnetization direction, respectively. The off-diagonal element pn represents the spontaneous or anomalous Hall resistivity (AHR) [3]. Conventionally, the anisotropy of the resistivity is expressed by the SMA ratio... 

---