Free energy and phase diagram of chromium alloys
- Department of Physics, North Dakota State University, Fargo, North Dakota 58105-5566 (United States)
- Solid State Division, P.O. Box 2008, Oak Ridge National Lab, Oak Ridge, Tennessee 37831 (United States)
The phase diagram of chromium alloys is remarkably rich. At the Neel temperature of 310 K, pure chromium undergoes a weakly first-order phase transition into an incommensurate spin-density wave (SDW) state. When doped with more than 0.2% manganese, this transition becomes second order and the SDW becomes commensurate. Over 25 years ago, Koehler [ital et] [ital al]. and Komura, Hamaguchi, and Kunitomi observed a first-order commensurate-to-incommensurate (CI) transition in CrMn alloys. The temperature of this CI transition decreased to zero as the manganese concentration increases from about 0.2% to about 1.5%. Using mean-field theory, we have constructed the free energy and phase diagram of chromium alloys in the presence of electron scattering. In the absence of scattering, the phase diagram allows a first-order phase transition from the incommensurate to the commensurate states with decreasing temperature. But if the damping is sufficiently large, the phase-separation curve flips from the right side of the tricritical point to the left. So within a small window of manganese concentrations, the commensurate state undergoes a first-order transition into the incommensurate state with decreasing temperature, in agreement with the experiments of Koehler [ital et] [ital al]. At zero temperature, we find a first-order phase transition from the incommensurate to the commensurate state with manganese doping, in agreement with the work of Komura, Hamaguchi, and Kunitomi. In the absence of damping, the zero-temperature energy gap [Delta](0) in the commensurate regime is independent of manganese concentration. But in the presence of damping [Delta](0) becomes an increasing function of the manganese concentration.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 7369219
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 48:6; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effects of an electron reservoir on the phase diagram of chromium alloys
Magnetic structure and paramagnetic dynamics of chromium and its alloys
Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
CHROMIUM ALLOYS
PHASE DIAGRAMS
BINARY ALLOY SYSTEMS
FREE ENERGY
MANGANESE ALLOYS
MEAN-FIELD THEORY
NEEL TEMPERATURE
ALLOY SYSTEMS
ALLOYS
DIAGRAMS
ENERGY
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
665000* - Physics of Condensed Matter- (1992-)
360102 - Metals & Alloys- Structure & Phase Studies