Magnetism inAu82.5Fe17.5

Abstract

The low steady-field susceptibility of ${\mathrm{Au}}_{82.5}$ ${\mathrm{Fe}}_{17.5}$ (either in the quenched or in the aged condition) measured as a function of increasing temperature after approximate-zero-field cooling to 4.2 K, using a specimen-field configuration with a low demagnetization factor, does not show any of the features often attributed to the presence of long-range ferromagnetism and to magnetic phase transitions. Under such conditions and measuring with a field of 9.6 Oe, the susceptibility has a well-defined maximum at ∼100 K. At a higher steady field the maximum shifts to a lower temperature. The alloy shows isothermal remanence up to at least 130 K and magneto-thermal-history effects typical of spin glasses up to about 110 K. Its behavior below ∼144 K indicates a gradual increase in the magnetic viscosity with decreasing temperature. The susceptibility maximum appears to arise through a kinematic effect and it does not signify a phase transition.