Magnetic properties and crystal structure of β-Ta

Atomic clusters and phase transitions in the metastable β-Ta phase between 4.2 and 293 K

“…is slightly non-linear at 4.2 K [5]. However, these studies did not associate the concentration of the clusters, N ∼ 10 20 1/mol, and their magnetic moments, m cl ∼ 1000 µ B , with any structural data.…”

“…The unusually low concentration of clusters (1 cluster per 200 unit cell) and large magnetic moment (1000 µ B ) of each cluster as obtained in [5] at 77 K can now be explained with the cluster model introduced in this study. Indeed, the length of the cluster is extending over many cells when the temperature approaches 65 K, temperature at which the cluster reaches an infinite length.…”

“…for H but irreversible for G. The χ(T )-dependence measured on powder samples [5] indicates a magnetic phase transition at 65 K ( fig. 2).…”

“…1) composite structure with indistinguishable lattice constants, but different space groups for the components, is characteristic of β-Ta. Based on the space groups of the components, it was shown that the phase transition 293 (RT-I modification) → 120 (LT-I modification) → 293 (RT-II modification) is reversible [5]), the electrical resistance R(T ) and the first derivative dR/dT . The R(T )-dependence was measured in situ for two polycrystalline bulks (cylindrical shape, 2-3 mm 2 in cross-section and 2-3 mm in length) using the four-point probe technique (measuring current 10 −4 A).…”

“…-Taking into account the contribution of the spin-spin interactions between magnetic moments of charges localized on the clusters owing to PLE on each single intra-cluster bond [5], the magnetic space groups can be related to the corresponding symmetry of β-Ta. In particular, the magnetic group of G should be a supergroup of H at the same temperature and should allow the existence of some clusters with opposite spins at the corresponding temperatures.…”