GIANT MAGNETORESISTANCE IN FE1-XCOX CR(001) TRILAYERS/

We have investigated the magnetic and magnetotransport properties of w edge-shaped Fe1-xCox/Cr/Fe1-xCox trilayers grown by molecular-beam epi taxy on Al2O3 (<1(1)over bar 02>) substrates with the Co concentration x ranging from 0 to 0.2. A completely antiferromagnetic (AFM) couplin g with zero remanence is obtained in both pure Fe/Cr and alloy Fe1-xCo x/Cr samples at a Cr thickness of about 10 Angstrom. The giant magneto resistance (GMR) of the AFM coupled Fe/Cr trilayer is about 5.5% at lo w temperatures. With increasing Co concentration, the GMR effect, Delt a rho/rho(s), decreases drastically, having an amplitude of only 0.7% at x = 0.2. In the pure Fe/Cr trilayer, there is a strong reduction of the GMR effect with increasing temperature. In contrast, the GMR of t he samples with alloy magnetic layers is only weakly temperature depen dent because of an increase of the net change of the magnetoresistance , Delta rho, with temperature. The strong decrease of the GMR effect i n the alloy trilayers is tentatively ascribed to the possible loss of the band matching of the minority-spin band, which is important in the Fe/Cr superlattice. The temperature dependence of Delta rho at finite temperatures can well be interpreted by introducing a positive linear temperature term together with a negative quadratic term, which are a ttributed to spin-dependent electron-phonon scattering and spin-flip e lectron-magnon scattering, respectively.