Spin-wave dispersion relations have been measured in high-symmetry directions for metallic Gd. Analysis shows that at least five interplanar constants are required for a satisfactory fit to the data. The energy gap at $q=0$ is unmeasurably small. In the $c$ direction the measured dispersion curve gives directly the Fourier-transformed exchange interaction $J(0)\ensuremath{-}J(q)$. This exhibits no other extreme value except that at the origin.

We report neutron measurements of the magnetic disorder scattering cross section for ${\mathrm{Ni}}_{0.8}$${\mathrm{Cu}}_{0.2}$. These indicate that the magnetic moment disturbance produced by Cu in Ni is essentially limited to first-neighbor effects.

Neutron-diffraction measurements have been made on single-crystal holmium at temperatures ranging from 4.2 to 120\ifmmode^\circ\else\textdegree\fi{}K in applied magnetic fields up to 22.3 kOe in order to study the magnetization process of this material. At low temperatures, the $b$ direction in the basal plane is an easy axis. For a field applied parallel to an $a$ direction, the moments are aligned parallel to the closest $b$ directions. At higher temperatures the effect of a field applied parallel to a $b$ direction is to transform the system to a $b$-axis ferromagnet after causing it to pass through one or two (depending upon the temperature) intermediate fanlike oscillatory structures. Similar oscillatory configurations are produced by the application of a field parallel to an $a$ direction. The $a$-axis ferromagnet is not produced in fields up to 22.3 kOe. A characterization of the four intermediate structures observed at 50\ifmmode^\circ\else\textdegree\fi{}K was made and schematic phase diagrams in the $H\ensuremath{-}T$ plane were extracted from the diffraction and magnetization data. Studies of the remanent state at 4.2\ifmmode^\circ\else\textdegree\fi{}K were made, and are reported.

Neutron-diffraction measurements have been made on single-crystal specimens of holmium at temperatures ranging from room temperature to 4.2\ifmmode^\circ\else\textdegree\fi{}K. Below the N\'eel temperature of 133\ifmmode^\circ\else\textdegree\fi{}K, the moments order in a helical structure in which the $c$ axis is the screw axis. The interlayer angle varies from about 50\ifmmode^\circ\else\textdegree\fi{} per layer at ${T}_{N}$ to 30.0\ifmmode^\circ\else\textdegree\fi{} per layer at 4.2\ifmmode^\circ\else\textdegree\fi{}K. Below about 20\ifmmode^\circ\else\textdegree\fi{}K the structure is a conical configuration in which there is a net moment of $1.7{\ensuremath{\mu}}_{B}$ parallel to the $c$ axis. The configuration of moments in the basal plane at 4.2\ifmmode^\circ\else\textdegree\fi{}K is a distorted helical one in which moments of $9.5{\ensuremath{\mu}}_{B}$ are bunched around the easy $b$ directions in the plane.

Neutron-scattering and magnetization measurements were made on a series of face-centered cubic $\mathrm{P}\mathrm{d}\ensuremath{-}3d$ and $\mathrm{N}\mathrm{i}\ensuremath{-}3d$ alloys to determine the distribution of magnetic moments in these ferromagnetic binary alloys. The specific alloys studied were: ${\mathrm{Ni}}_{3}$Co, NiCo, ${\mathrm{Pd}}_{3}$Co, PdCo, ${\mathrm{Pd}}_{3}$Fe (ordered and disordered), PdFe, ${\mathrm{Pd}}_{0.93}$${\mathrm{Fe}}_{0.07}$, and ${\mathrm{Pd}}_{0.97}$${\mathrm{Fe}}_{0.03}$. Magnetic moments of about 3.0, 1.8, and 0.6 Bohr magnetons per atom were found for Fe, Co, and Ni, respectively, and these were essentially independent of concentration. The average Pd moment varies with concentration and approaches a maximum of about 0.4 Bohr magnetons per atom in the concentrated alloys.

A neutron-diffraction study of the heavy rare earths Tb, Dy, Ho, Er, and Tm diluted with yttrium and of Tb with lutetium is reported. The modulated antiferromagnetic structures of the rare-earth metals are found to exist in the alloys, but the ferromagnetic phases of Tb and Dy are destroyed with small admixtures of Y. The N\'eel temperatures of the alloys and the pure metals are found to be a universal function of the average of the square of the spin projection on $J$, given for these heavy-rare-earth alloys by $\ensuremath{\xi}=c{(g\ensuremath{-}1)}^{2}\ifmmode\times\else\texttimes\fi{}J(J+1)$, where $c$ is the atomic concentration of rare earth. The value of the interlayer angle $\ensuremath{\omega}$ at ${T}_{N}$ which is related to the wavelength of the modulation of the magnetic structure is also found to be a universal function of $\ensuremath{\xi}$, and the temperature variation of $\ensuremath{\omega}$ decreases with decreasing $\ensuremath{\xi}$ so that $\ensuremath{\omega}$ approaches a temperature-independent value of about 50\ifmmode^\circ\else\textdegree\fi{} per layer for small $\ensuremath{\xi}$, regardless of the magnetic ion in the alloy.

Mo${\mathrm{F}}_{3}$ becomes antiferromagnetic below 185\ifmmode^\circ\else\textdegree\fi{}K with a spin-only magnetic moment corresponding to $S=\frac{3}{2}$ and a magnetic structure which can be correlated with coupling rules applicable to the iron-group trifluorides. These results, together with the absence of observable magnetic neutron scattering from Pd${\mathrm{F}}_{3}$ and Ru${\mathrm{F}}_{3}$, suggest that Hund's rule does not apply to ions in the $4d$-transition series.

Neutron diffraction observations have been made on powder samples of Cr${\mathrm{F}}_{2}$ and Cr${\mathrm{Cl}}_{2}$ from 298\ifmmode^\circ\else\textdegree\fi{} to 4.2\ifmmode^\circ\else\textdegree\fi{}K. These materials, which have crystal structures similar to rutile but distorted from tetragonality, become antiferromagnetic at low temperatures with different magnetic structures. For Cr${\mathrm{F}}_{2}$ the magnetic unit cell is identical with the chemical cell and the moments at the corner sites are directed oppositely to those at the center of the cell. The magnetic unit cell of Cr${\mathrm{Cl}}_{2}$ requires doubling of the $b$ and $c$ axes of the orthorhombic chemical cell and the structure consists of ferromagnetic (011) planes with adjacent planes antiparallel. In neither case were the intensities compatible with a magnetic axis directed along a simple crystallographic direction. Unique magnetic axes could not be definitely established but the data suggest that they lie parallel to the longest Cr-F and Cr-Cl bonds. N\'eel temperatures of 53\ifmmode^\circ\else\textdegree\fi{} and 20\ifmmode^\circ\else\textdegree\fi{}K were observed for Cr${\mathrm{F}}_{2}$ and Cr${\mathrm{Cl}}_{2}$, respectively.