INFLUENCE OF THE VALENCE OF THE SUBSTITUTED CATIONS ON THE ELECTRICAL-PROPERTIES OF THE MAGNETICALLY MODULATED SPINELS ZN1-XCUXCR2SE4, ZN1-XGA-2/3XCR2SE4

The experimental results concerning the electrical conductivity and the Seebeck effect in the spinel series Zn1-xAxCr2Se4 (A=Cu,Ga2/3) are presented. They serve as a basis for the calculations of both the concentration and the mobility of the current carriers as well as of the Fermi energy in the temperature range of 70500 K. The results suggest that in the spinel series under study the changes of the electrical conductivity are connected with the changes of both the concentration and the mobility of the current carriers. The strong relation of the magnetic and electrical properties of the spinels under study is emphasized. It turns out that the large electrical conductivity is accompanied here by both the ferromagnetic ordering of the magnetic moments and the partial degeneracy of the semiconductor state, whereas the small electrical conductivity is accompanied here by both the domination of the antiferromagnetic component of the ordering of the magnetic moments and the compensation of the semiconductor state. © 1990 The American Physical Society.