Magnetic Mysteries of Neodymium: Nanometer-Scale Spin Textures Revealed by SANS

The rare earth neodymium exhibits exceedingly complex magnetic order and series of phase transitions. In this talk, we present results from small-angle neutron scattering (SANS) measurements as a function of temperature and applied magnetic field to study magnetic correlations on nanometer length scales in Nd. The SANS measurements reveal a set of new modulation vectors that characterize the ordered spin configuration. These spin textures exhibit changes in magnitude and direction that are phase dependent. Between 5.9 and 7.6 K, the additional modulation vector has a magnitude $Q$ = 0.12 \AA$^{-1}$ and is primarily due to order of the Nd layers which contain a center of inversion. In this region of the phase diagram, the SANS measurements also identify a phase boundary at $\approx$1 T which was not previously seen in thinner samples. An important feature of these modulation vectors is that they indicate the presence of nanometer length scale spin textures which are likely stabilized by frustrated Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions.