The spin wave stiffness constant D was determined from the temperature dependence of the magnetization for Co–B–Si glasses in the range 70% Co to 80% Co. We found that: (a) varying the amount of Si has a strong effect on D, (b) introducing Si into Co–B initially increases D (which may be interpreted as an increase of atomic order) with a maximum for about 5% Si and then decreases for larger amounts up to 15% Si, (c) most of our samples have a dependence of D on the Curie temperature TC for varying composition similar to that of the Fe–Ni–B–P glasses; however, three samples have dependence similar to that of Co–X glasses (X=P+B or P), (d) the decrease of magnetization with T can be described well, for most of investigated Co–B–Si samples, by a Heisenberg model with short-range interaction.
m the last few years the thermoelectric power OL was measured in boron crystals over a wide temperature range (1 to 7). All results for samples of various purity indicate a p-type conductivity. The most representative data are plotted in Fig. 1. Two types of temperature dependence of Q may be seen. Above 400 to 5OO0K cu; decreases with temperature as 1/T (for samples of high purity). This is the usual behaviour for semiconductors when the carrier concentration depends exponentially on the reciprocal temperature as exp(-e/BkT). The activation energy & obtained from the slope doL/d(l/T) is about 1 . 4 eV, which is close to the activation energy of the electrical conductivity at high .temperatures and to the energy gap found from optical measurements. So it may be concluded that the thermoelectric power in this temperature range is caused by the diffusion of current carriers due to the gradient of their concentration in the sample.In samples of high concentration of impurities and in pure samples at lower temperatures different temperature dependence has been observed: OG increases with increasing temperature. Such a behaviour is observed in metals and in semiconductors in the impurity conduction range at constant carrier concentration. In both cases the carrier concentration is independent of temperature and the thermoelectric power is caused by a kind of thermodiffusion i. e. is due to the gradient of carrier mobility in the sample. The similar interpretation of his data has been presented by Uno (l)*who has found an increase of a with temperature in polycrystalline boron samples with high concentration of impurities. Using a simple theory he deduced that in his case the carrier concentration remained nearly constant and the mobility varied exponentially with the reciprocal temperature. Such temperature dependence of mobility is im good agreement with the idea presented by many authors (8 to 11) that in boron electrical conductivity is due to the thermally activated hopping processes between some local states. It may be supposed that this kind of transport takes place also in
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