Magnetoresistance and nanoscopic magnetic coherence in some frustrated ferromagnets

Measurements of magnetic and magnetotransport properties of frustrated metallic ferromagnets are combined to get information on their equilibrium spin pattern over distances of the order of the nanometer. The considered systems are concentrated, chemically homogeneous solid solutions of one or more transition metals in a host diamagnetic metal; competing interactions produce a significant magnetic frustration and a ultrashort ferromagnetic coherence length over an extended range of temperatures. The isotropic negative magnetoresistance exhibited by these systems is instrumental for obtaining information on changes of the spin pattern on the nanometer scale. Recent magnetic and magnetotransport data obtained on three frustrated ferromagnets (Au(80)Fe(20), Au(70)Fe(30), and Cu(60)Fe(20)Ni(20)) are briefly discussed. The magnetoresistance behavior of these systems is related to the changes of the magnetic coherence length by effect of both temperature and applied magnetic field.