First Order Transition of the Spin Density Wave State in Cr–Si Alloys

Abstract

Thermal expansivities of Cr–Si alloys containing small amounts of Si up to 2.0 at.% were measured above 100 K. For alloys with Si atoms ranging from 1.0 to 1.4 at.%, two first order transitions are observed successively for the transitions from the paramagnetic (P) state to a commensurate (C) spin density wave (SDW) state and from the CSDW to an incommensurate (I) SDW state with decreasing temperature. The tricritical point is assigned to T_N^*=245 K and C^*=0.975 at.% Si, where three loci of the P–I, P–C and C–I transitions concurred together satisfying the condition of the second order transition. On the basis of the two band model, just one of the four outer electrons of Si is estimated to flow into the magnetic bands of Cr.