MAGNETORESISTANCE OF THE MAGNETICALLY ORDERED ICOSAHEDRAL QUASI-CRYSTALS AL-PD-MN-B

The transverse magnetoresistance has been measured for the newly disco vered magnetically ordered icosahedral quasicrystals Al70-xPd15Mn15Bx (x=0,2,4,6,8,10). Experiments were conducted at 4.2 K in magnetic fiel ds up to 5.5 T. The results showed a systematic change as a function o f boron concentration. The magnetoresistance for x=0,2,4,6 showed a ne gative field dependence which became weak with increasing x. The sampl es with x=8,10 showed a negative magnetoresistance at low fields, whic h became positive for higher applied fields. The minimum in the magnet oresistance shifted to lower field value with increasing boron content (to about 0.5 T for 10 at. %B). The analysis of the results has been based on the theory of three-dimensional weak localization, with a str ong influence of spin-orbit scattering. The magnetoresistance is negat ive for low boron concentration due to weak spin-orbit scattering, and is positive for high boron concentration due to strong spin-orbit sca ttering.