SPIN GLASS AND FERRIMAGNETISM IN YFexAl12 - x(4 less than equivalent to x less than equivalent to 6).

Magnetization and **5**7Fe Moessbauer studies of YFe//xAl//1//2// minus //x, x equals 4. 0, 4. 5, 5. 0, 5. 5 and 6. 0 of the tetragonal ThMn//1//2 structure, at temperatures 4. 1 to 350 K have been performed. Studies here reveal that YFe//4Al//8 and YFe//6Al//6 are indeed an antiferromagnet and a ferrimagnet, respectively. However, YFe//xAl//1//2// minus //x, x equals 4. 5, 5. 0, 5. 5 are ferrimagnets below T//c (105, 165 and 225 K, respectively) down to T//G (T//G**0 equals 84, 82 and 128K, respectively). Below T//G the systems exhibit all the features typical to spin glasses. Large differences between zero and field cooled magnetization; high thermoremanent and isothermal remanent magnetizations; time dependence of remanence magnetization, magnetization dependence on cooling rates and unusual hysteresis curves. A particular striking observation is that the spin glass transition temperature which decreases with external magnetic field, follows very accurately the 2/3 power law.