High pressure magnetic phase diagram of an antiferromagnetic Cr+0.50 at.% Re alloy single crystal

The pressure-temperature magnetic phase diagram of a Cr + 0.50 at.% Re allo y single crystal has been obtained from high pressure ultrasonic wave veloc ity measurements. A triple point exists on the magnetic phase, diagram wher e the incommensurate (I) and commensurate (C) pin-density-wave (SDW) phases coexist with the paramaguetic (P) phase. The ISDW-CSDW phase transition is a first-order transition while the CSDW-P and ISDW-P Neel transitions ale continuous. Both the ISBW-CSDW/CSDW-ISDW and CSDW-P phase lines are nonline ar with exceptionally large pressure derivatives near the triple point pres sure. Thermal expansion measurements on the crystal together with the high pressure measurements give a latent heat nf 13.7 J mol(-1) associated with the first-order ISDW-CSDW phase transition. Thr temperature dependence of t he magnetovolume, Delta omega, has been observed to fit the equation \ Delt a omega \ = A(0) + A(1)T(2) + A(2)T(4) fairly well in the CSDW phase. (C) 2 001 Elsevier Science B.V. All rights reserved.