Neutron study of magnetic correlations in rare-earth-free Mn-Bi magnets
Abstract
We report the results of an unpolarized small-angle neutron scattering (SANS) study on Mn-Bi-based rare-earth-free permanent magnets. The magnetic SANS cross section is dominated by long-wavelength transversal magnetization fluctuations and has been analyzed in terms of the Guinier-Porod model and the distance distribution function. This provides the radius of gyration which, in the remanent state, ranges between about 220-240 \, nm for the three different alloy compositions investigated. Moreover, computation of the distance distribution function in conjunction with results for the so-called s-parameter obtained from the Guinier-Porod model indicate that the magnetic scattering of a Mn45Bi55 sample has its origin in slightly shape-anisotropic structures.