Magnetoresistance of rare earth iron garnets

The magnetoresistance of bulk and epitaxial films of YIG(Si) has been previously reported by us (Ref. 10). These results can be summarized by the cubic expression ΔR/R=kl(α2iβ2i–αiαjβiβj) where kl at 300°K is between −0.002 and −0.02 and essentially independent of the value of the applied field once the sample is saturated. Similar results have now been obtained for Eu3Fe5O12 (Si) and Eu2.9Lu0.1Fe5O12(Si). The behavior of Tb3Fe5O12(Si) is dominated by additional phenomena. The relatively large field independent term observed in YIG(Si) is small here. However there is a large, isotropic field dependent term and ‖ΔR‖ increases linearly with H. The value of (1/R) (dR/dH) is positive at 300°K and increases with decreasing T. At the compensation temperature this quantity abruptly changes sign and then decreases rapidly with decreasing T. The absolute value of (1/R)(dR/dH) is continuous except for a break right at the compensation temperature. (It is interesting to note that the addition of Si in the sample dis...