Quasi-cubic Sites Research Articles

Magnetic properties and spontaneous magnetostriction of a Sm 2Co 7 single crystal

The high-field magnetization and the lattice parameters of the intermetallic compound Sm 2Co 7 have been studied on single-crystal samples in a wide temperature range. The compound is a highly anisotropic ferromagnet having μ S = 10.1μ B/f.u., T c = 670 K and uniaxial magnetic anisotropy above 68 K. Below 68 K, a spontaneous spin reorientation of the axis-cone type occurs and the cone angle reaches 15° at 4.2 K. The Sm atoms on the quasicubic sites are considered to be responsible for the spin reorientation. The magnetic ordering is accompanied by positive spontaneous magnetostrictive strains in the basal plane and along the c axis which reach at 5 K 2.1 × 10 -3 and 3.6 × 10 -3, respectively. That corresponds to a spontaneous volume magnetostriction 7.8 × 10 -3. The spin reorientation is accompanied by an additional negative volume anomaly -0.9 × 10 -3.

Magnetic excitations and phase transitions in UPd 3

The magnetic excitations in single crystal UPd 3 have been studied by inelastic neutron scattering. At 1.8 K, we find at a general wave vector, four modes below 3 meV which we ascribe to crystal field-like excitations on the quasi-cubic sites. Their temperature dependence has been measured and the results are explained in terms of a quadrupolar transition at T 1 = 6.5 K, followed by a magnetic transition at T 2 = 4.5 K.

Thermal expansion anomalies and spontaneous magnetostriction in Tm 2Co 7

The temperature dependencies of the lattice parameters and magnetization have been studied in the intermetallic compound Tm 2Co 7. Magnetic ordering is accompanied by spontaneous magnetostriction in the basal plane and along the c axis (2.0 × 10 −3 and 2.7 × 10 −3 respectively at 5 K). This corresponds to a volume effect ω s = 6.6 × 10 −3. The Tm atoms on the quasi-cubic sites are considered to be responsible for the spin reorientation from the uniaxial type of magnetic anisotropy above 45 K to the cone of easy axes below this temperature, which is explained by magnetoelastic effects. In the cone range a large orthorhombic distortion ϵ (up to −3.5 × 10 −3 at 5 K) is observed. The additional volume anomaly δω s = −1 × 10 −3, which accompanies spin reorientation, can be explained by the anisotropy of the magnetic moments of the thulium and cobalt sublattices.