Temperature Variation of the Magnetic Susceptibilities of Antimony-Tin Alloys

The principal magnetic susceptibilities of single crystals of pure antimony and of antimony-tin alloys up to 4.1 atomic percent tin have been determined in the temperature range 77°K to room temperature. The measurements were made with a modified Sucksmith-Jackson ring balance. It is found that the diamagnetic suspectibility perpendicular to the trigonal axis (${\kappa }_{\perp }$) is practically independent of temperature for all the alloys. The susceptibility parallel to this axis (${\kappa }_{\parallel }$) decreases in magnitude with increase in temperature, both for alloys in which ${\kappa }_{\parallel }$ is diamagnetic and those in which it is paramagnetic, with one exception, the alloy of 1.06 atomic percent tin. A suitable correction for the temperature-independent diamagnetic susceptibility of the lattice ions brings this exception into agreement with the others. The experimental values of ${\kappa }_{\parallel }$ are compared with Stoner's expressions for the susceptibilities of free electrons, on the assumption that ${\kappa }_{\parallel }$ is due to the electrons overlapping into the second Brillouin zone. Good agreement is obtained by adjusting the parameter ${\zeta }_0$, the upper limit of the Fermi distribution, and the degeneracy temperature of these electrons is found to be approximately 475°K, about 0.25 of what it would be for perfectly free electrons. This indicates that the effect of the lattice field is to suppress the value of ${\zeta }_0$ by increasing the density of electronic energy levels. Values of the effective masses of the electrons, which occur as parameters in the energy equation, are computed, and the energy interval between the bottom of the second Brillouin zone and the top of the Fermi distribution is estimated as about 0.04 ev.