Synthesis of Rare Earth Compounds and Study of Their Magnetic Optical and Semiconducting Properties
Final technical rept. 30 Jun 1970-30 Jun 1971
IBM THOMAS J WATSON RESEARCH CENTER YORKTOWN HEIGHTS NY
Pagination or Media Count:
Considerable information has been obtained on the nature of vapor- solid equilibria in EuO, EuS and EuSe. Crystal growth experiments and Knudsen effusion with mass spectrometric analyses show that EuS vaporize to yield essentially equal pressures of Eu and chalcogen in the vapor phase. In contrast EuO has been shown to be in equilibrium with only Eu vapor. A study of the reaction between H2S and Eu2O3 was carried out to determine the amount of residual oxygen in EuS as a function of reaction temperature. Samples produced at 1250-1300C in flowing H2S were found to contain less than 75 ppm oxygen. The use of this material resulted in the growth of more perfect EuS single crystals with a significantly lower oxygen content. Magnetic measurements for the system Eu1-xGdxS show ferromagnetic properties with temperatures up to three times that of insulating EuS. Surprisingly, however, the low temperature saturation moment decreases with Gd concentration. It is shown that the glass forming region in divalent europium chalcogenides can be extended beyond 50 mole EuO and that it is possible to introduce trivalent rare earth metals as potential dopants into these systems. It has been demonstrated that the insulator-metal transition found in EuO is caused by an exponentially changing carrier concentration with an activation energy which decreases linearly with increasing magnetization.
- Solid State Physics