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a shallow minimum in its variation with 68 (or composition) in the competition region. IV. CONCLUSIONSThe room temperature magnetoresistance data for the germanium-silicon alloys can be explained by a conduction band of L111) spheroids for alloys with less than ten percent silicon in germanium. However, the data for alloys of ten to seventeen percent silicon show a diferent anisotropy, not in accord with the assumption of one set of spheroids. These data are fitted satisfactorily by a conduction band made up of two sets of spheroids, with an energy separation varying with compositionone set having four L111)-oriented spheroids, the other having six L100j-oriented spheroids. This is in agreement with the alloy band structure suggested by Herman' to explain the variation with composition of the optical band gap. 7 This analysis does not yield unique values for the effective masses of the spheroids. However, the effective masses which fit the data for germanium arid sihcon satisfy the magnetoresistance symmetry condition for the ten to seventeen percent silicon alloys. An analysis of the data to yield the energy separation of the two bands as a function of composition depends sensitively on the scattering behavior in the alloys. If the scattering in each band is assumed independent of the other, the observed Hall mobility in the competition region is only about two-thirds that expected from an analysis of the magnetoresistance. The mobilities can be correlated with the magnetoresistance if some interband scattering is assumed. Such scattering lowers the band mobilities but leaves the magnetoresistance symmetry conditions unchanged.Dilute alloys of Mn in Cu are expected to show marked effects of the exchange interaction between the Ms ion core electrons of the Mn atoms and the 4s conduction electrons of the crystal. The simple model leads to the prediction of indirect exchange ferromagnetism; electronic Knight shift of the electron spin resonance line; nuclear Knight shift of the copper nuclear resonance; electron spin relaxation by the coupling with the conduction electrons; and a contribution to the electrical resistivity by the Elliott-Schmitt mechanism. The observed width of the electron spin resonance line suggests that the sd' exchange interaction may be of the order of 0.2 of the interaction in the free ion. The dilute alloys appear to be antiferromagnetic, but with a ferromagnetic interaction also present which is rather stronger than calculated on the indirect exchange model. An unexpected experimental result is that the nuclear Knight shift is unaffected by the presence of Mn, suggesting that the conduction electron magnetization by the sd coupling is less than 1/50 of what might be expected.' 'T occurred to us that it might be profitable to studỹ~b y electron spin resonance methods the electronic properties of metallic alloys. We were particularly interested in observing the eGect on the conduction electrons of the host metal when a low concentration of a second component is added. For several reasons it...

A pulsed X-band electron paramagnetic resonance spectrometer suitable for observing spin echoes in the sub-microsecond time domain has been designed and operated. Cryogenic apparatus makes possible measurements in the 300−1.6°K temperature range. System design considerations are discussed and circuit schematics are presented. Results of measurements of the spin-lattice relaxation time T1 and the spin-spin relaxation time T2 are reported for several paramagnetic substances. Application of such instrumentation to information storage is discussed.

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The intensities of paramagnetic resonance lines in SrTi0 3 have been correlated to the iron concentrations. Evidence for attributing the origin of the resonance in titanates to iron impurities (Fe 3+ ) rather than to the domain structure was obtained. In SrTi0 3 , resonance experiments over the temperature range 300°K to 1.9°K show a slow continuous increase of the tetragonal component of the crystalline field down to the ferroelectric region. From intensity considerations the absolute signs of the crystalline splitting parameters have been determined.