MAGNETIC STUDIES OF ANNEALED AND ALLOYED CHROMIUM BY NEUTRON DIFFRACTION

The onset of long-range magnetic order in a heavily crushed powder of chromium takes place at 450°K, below which a simple antiferromagnetic structure AF0 exists. With reduction of temperature it gradually transforms into the structure AF1 which is incommensurate with the unit cell. The subsequent spin-flip transition (AF1 -> AF 2) occupies a temperature range and is incomplete even at 4·2°K. When the sample is annealed the AF0 structure becomes less prominent and the temperature ranges of both the spin-flip and commensurate-incommensurate transitions decrease, until the 'normal' (single-crystal type) behaviour is reached. Study of a chromium-1/2% rhenium sample gives an indication of the nature of the AF0-AF1 transition.