A detailed study of Mn-rich γ-phase ${\mathrm{Cu}}_{100\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$ with Mn concentration up to 83 at. % has been carried with use of ac-susceptibility, dc-magnetization, and electrical-resistivity measurements. All the concentrated alloys have shown the signature of the spin-glass phase below certain temperatures with antiferromagnetic short-range order. The alloys with more than 73 at. % of Mn have long-range antiferromagnetism at higher temperatures. An earlier neutron diffraction study has already proved the existence of long-range antiferromagnetism at low temperatures for alloys with Mn above 72 at. %. Thus we conclude that ${\mathrm{Cu}}_{100\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$ is a spin glass with short-range antiferromagnetically coupled clusters up to 73 at. % Mn and beyond that it exists in a mixed spin-glass and long-range antiferromagnetic state below certain temperatures. This may be called a reentrant antiferromagnetism since the high-temperature phase is a pure long-range antiferromagnetic phase. We have constructed the magnetic phase diagram for the whole range of composition on the basis of our magnetic study and the earlier neutron diffraction measurements. We have found a ${\mathit{T}}^{2\mathrm{-}}$${\mathit{T}}^{5/2}$-type of magnetic contribution to the electrical resistivity in the spin-glass regime for all the alloys. We propose a scheme to isolate the magnetic contribution to the resistivity for all temperatures and apply it to a nondilute system.

• Received 16 June 1992

DOI:https://doi.org/10.1103/PhysRevB.46.8958