EFFECTS OF AN ELECTRON RESERVOIR ON THE PHASE-DIAGRAM OF CHROMIUM-ALLOYS

The phase diagram of chromium alloys sensitively depends on the presence of an electron reservoir. With the formation of a spin-density wave (SDW), electrons are depleted from the nested electron-hole surfaces and for a finite reservoir the chemical potential will decrease. If the power p of the electron reservoir were infinite, then the chemical potential would remain constant :Ind lightly doped CrMn alloys would experience a first-order transition from an incommensurate (I) to a commensurate (C) SDW state with decreasing temperature. With a power less than about 10, the reservoir will flip the phase boundary from one side of the triple point to the other, allowing a commensurate to incommensurate transition with decreasing temperature as observed experimentally. A finite reservoir also suppresses the first-order jumps in the SDW order parameter and wave vector. When p less than or equal to 2, the CI transition is second order for all temperatures. When p > 2, the transition is second order near die triple point but first order at lower temperatures.