Electrical resistivity in spin glass C uMn

Abstract

The electrical resistivity is discussed, providing a direct measurement of the critical exponent β for a spin glass CuMn. CuMn alloys with magnetic impurity concentrations ∼0.7–4.5 at. % exhibit the characteristic spin glass cusp in low field ac susceptiblity at temperature TF. The magnetic contribution to the resistance of this alloy increases with temperature below Tf and is constant above Tf. By using the exchange interaction between the conduction electrons and the unpaired electrons localized on the Mn ion as a perturbation and by applying the Boltzmann transport equation, the electrical resistivity is shown to be related to the order parameter q. Below the freezing temperature, scattering can be caused by deviation of the spin from its ground state. As the temperature rises, the resistivity will increase, too. Above the freezing temperature, each spin behaves perfectly independently and gives rise to a constant resistivity. So the critical exponent β of spin glass order parameter q can therefore be determined by fitting the theory to measured data. It also can be shown that specific heat is related to the temperature derivative of ρmag(T) for ordered magnetic moment material.