Magnetic Form Factor of Thulium Metal

Abstract

The magnetic form factor of thulium at 4.2\ifmmode^\circ\else\textdegree\fi{}K has been measured with polarized neutrons. With the exception of the two innermost reflections, the form factor is in excellent agreement with the theoretical $4{f}^{12}$ form factor. At low angles an additional contribution to the form factor is present. We have interpreted this as $5d$-like conduction-electron polarization, although the magnitude is unexpectedly large.