Magnetic Form Factor of Chromium

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Abstract
Neutron‐diffraction measurements of the magnetic Bragg peaks from single crystals of chromium with small additions of manganese have been used to determine the magnetic form factor of chromium. The addition of manganese simplifies the experimental problem by stabilizing the simple antiferromagnetic structure. A single magnetic peak is observed at reciprocal lattice positions, rather than a group of six satellite peaks as in pure chromium. Also, manganese increases the Néel point so that the measurements were performed at room temperature. The results are in good agreement with free‐atom Hartree‐Fock calculations for the chromium 3d electrons. A definite indication of nonspherical symmetry was obtained by comparing the (221) and (300) reflections. These reflections come at the same scattering angle, yet the (221) intensity is larger by about a factor of six. This indicates a t2g population of 79%, compared to 60% for a spherical spin distribution. The results are independent of manganese concentration over a range from 1.7 to 4.1 at. %.