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 ρ of the electron reservoir were infinite, then the chemical potential would remain constant and 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 ρ≤2, the CI transition is second order for all temperatures. When ρ>2, the transition is second order near the triple point but first order at lower temperatures.