Antiferromagnetism in Dilute Iron Chromium Alloys

The magnetic properties of single crystals of Cr alloys containing a small amount of Fe have been studied mainly by neutron diffraction. The alloys with less than 1.5 at.% Fe have been found to have the same magnetic structure as that of pure Cr. With increasing Fe concentration, which corresponds to an increase of the electron to atom ratio, the Néel temperature decreases, the wave vector of the sinusoidally modulated spin density wave increases, while the magnetic moment remains almost constant. The spin-flip temperature also decreases rapidly. The alloys with concentrations between 2 and 4 at% Fe have a simple antiferromagnetic structure at low temperatures, and the first order transition from the antiferromagnetic state to a sinusoidal spin state has been observed with increasing temperature. When the concentration of Fe exceeds 4 at%, the alloy is a simple antiferromagnet up to the Néel temperature. These results are discussed on the basis of the two band model.