Showing papers by "W. C. Koehler published in 1963"

Neutron diffraction investigation of the magnetic properties of compounds of rare-earth metals with group v anions

Abstract: The magnetic properties of heavy rare-earth compounds with the NaCl-type structure have been investigated at temperatures between 295 and 1.3\ifmmode^\circ\else\textdegree\fi{}K by neutron diffraction experiments on powdered specimens. All of the nitrides except TmN have a net ferromagnetism at low temperatures, but the diffraction patterns indicate a complicated type of magnetic order. HoP also has an unusual magnetic structure at low temperatures and this structure is presumably stabilized by dipole forces. The other phosphides, antimonides, and arsenides were found to have magnetic ordering transitions to the Mn-O type of antiferromagnetic structure. Low values of the atomic moments and large magnetic anisotropies in the ordered magnetic structures indicate the effects of crystal field interactions at low temperatures.

Some Magnetic Structure Properties of Terbium and of Terbium‐Yttrium Alloys

Abstract: Neutron diffraction studies have been made on single‐crystal and polycrystalline specimens of terbium. Earlier magnetic and thermal measurements have indicated a transformation to an ordered magnetic state at approximately 230°K, and a subsequent order‐order transformation at approximately 220°K. The neutron measurements show that in the narrow antiferromagnetic region, the magnetic structure of terbium is a helical structure. The interlayer turn angle varies from 20.5° per layer at the Neel point to 18.5° per layer at the lower transition. At this lower temperature the structure transforms, in the absence of any external applied field, to a classical ferromagnetic structure in which the moments are in, or nearly in, the planes perpendicular to the hexagonal axis. At very low temperatures the magnetic moment per atom is very nearly 9.0 Bohr magnetons, the value expected for the ordered tripositive ion. Neutron diffraction measurements have also been made on a series of alloys of yttrium and terbium in order to study the influence of magnetic dilution on the magnetic properties of the rare‐earth metals. Introduction of yttrium into terbium reduces the Neel temperature and broadens the range of existence of the helical phase. At 30‐at. % yttrium and above, the spontaneous transformation to the ferromagnetic state is not observed, for zero applied field, even for temperatures as low as 4.2°K. As in pure terbium the interlayer turn angle ω of the helical structure in the alloys varies with temperature, but the slope of the ω vs temperature curve becomes smaller with increasing yttrium concentration.

Atomic Magnetic Moments in Dilute Iron—Palladium Alloys

Abstract: Neutron scattering and magnetization measurements were made on dilute iron—palladium alloys to determine the existence and magnitude of the magnetic moments of the constituent atoms. This determination was made by the combination of the difference in the aligned magnetic moments obtained from the ferromagnetic diffuse neutron scattering and the average ferromagnetic moment per atom obtained from the saturation magnetization measurements. Data were taken on two alloys which contained 3 and 7 at. % Fe. The following results were obtained: Pd0.97Fe0.03: 3.0±0.2 μB/Fe, 0.15±0.01 μB/PdPd0.93Fe0.07: 3.0±0.2 μB/Fe, 0.27±0.02 μB/Pd.