Correlation between magnetoresistance and magnetization inAgMn andAuMn spin-glasses

Magnetization has been measured between 2 and 77 K and mostly up to fields of 20 kOe in AgMn (1.1 and 5.4 at.%) and AuMn (1.8 and 4.6 at.%) spin-glass samples where the transverse magnetoresistance was measured earlier. It is found, for the first time, that over a wide range of temperature and magnetic field the negative magnetoresistance varies as the square of the bulk magnetization resulting in an universal curve in the spin-glass regime. The constant of proportionality is independent of the Mn concentration. A theoretical justification is provided in terms of existing theories.