To explain t!>e well known anomaly in the specific heat of solid hydrogen below lOOK Schaferl } proposed a model in which each molecule is immersed in an axially symmetric field of the type -AP20(COS IJ),IJ being the angle betw.een the molecular axis and the crystalline hexagonal axis.It is interesting, therefore, to see how the newly developed method of nuclear resonance throws light· 1.0 (l.g 0.6 OH V'r <--0.2 0 {oK' fl Fig. 1. T em perature dependence of characteristic time .. c (The slope indicates the height of barrier. which hinders molecular rotation.)at University of

We use a model for ferromagnets such that the electrical current is carried by 4s (or 6s) electrons which are assumed to be described in band scheme and the unpaired electrons (3d or 4J) are assumed to be localized on the lattice points. In the temperature region far below the Curie point the spin-disorder in spin orientation, which can be naturally described in terms of spin waves, gives rise to the scattering of conduction electrons through the s-d interaction and accordingly contributes to the anomalous part of the resistivity of type 1'2, which agrees fairly well with the experimental results both in order of magnitude and in temperature dependence. The effects of the lattice vibration are also discussed and turn out to give only the small additional contribution of type 1'5. JJ'" .and is easily shown to be independent of Rn. where ~n (r) and ~Ir. (r) are the wave functions of unpaired electron localized on the n-th lattice point and conduction at Pennsylvania State University on May 27, 2015 http://ptp.oxfordjournals.org/ Downloaded from * It is suggested by Wilson that if the energy surfaces are not spheres it is possible for s-and d-surfaces to cut one another in some directions in k-space, and in the neighbourhood of these directions long lattice waves may be: able to participate in the s-d transition. qUUtl is then zero. These circumstances, however, seem to occur only in a very special case, and in general there is a non-zero value of wave vector for the phonon which is required to produce an s-d transition.

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