Magnetic and Crystal Structures of ErC2 at 297–2°K

Neutron‐powder diffraction measurements show that the tetragonal body‐centered ErC2 becomes antiferromagnetic below 19 ± 2° K. The moment alignment is governed by several narrowly dispersed, incommensurate transverse magnetization waves. The major modulation waves propagate along the a axis and are polarized in the b axis direction. The magnetization wavelengths are 5.78, 5.4, 6.7, and 7.1 A, and the amplitudes are respectively 6.55, 2.2, 2.1, and 1.6 μB at 4.2°K. The ferromagnetic alignment in the plane perpendicular to a is slightly altered by several long‐periodicity modulations propagating along the b and c axes. A commensurate, antiferromagnetic wave also participates in the moment alignment below 10 ± 3° K. The commensurate wave is represented by setting the wavelength equal to the a spacing in the incommensurate wave mode. The commensurate moment is 2.5 μB at 4.2°K. The root‐mean‐square value of all the moment amplitudes is 7.8 μB at 4.2°K and increases to 7.9 μB at 2°K. These features are likely c...