Electrical transport properties and preparation of the metal-ammonia compound lithium tetraammine

Abstract

On specimens of the compound lithium tetraammine, Li(NH 3) 4, the resistance from 10 to 100°K and the magnetoresistance at 4.2 and 1.66 K have been measured. Measurements were made using a probeless, mutual inductance technique. Specimen preparation and aspects of the measurement technique used in preparing well mixed, homogeneous specimens are described. The resistivity shows several anomalies in the solid phase, one of which has also been observed in thermal measurements and is associated with a transition from an fcc to an hcp structure. The second, near 69 K, has not been observed in thermal measurements. It is suggested that this anomaly is characteristic of the compound Li(NH 3) 4 and may be a Martensitic or magnetic transition. The magnetoresistance is large with a marked decrease in slope above 50 kG. These results are compared with standard galvanomagnetic theory for compensated and uncompensated metals. In conjunction with arguments based on a free electron construction of the Fermi surface, it is concluded that lithium tetraammine is probably an uncompensated metal with a high proportion of carriers in open orbits.