Praseodymium diantimonide is an inorganic compound of praseodymium and antimony with the chemical formula PrSb2. It is a layered metallic compound that crystallizes in the orthorhombic SmSb2-type structure. PrSb2 undergoes a charge-density wave transition near 100 K and orders antiferromagnetically near 5 K.
Preparation Praseodymium diantimonide can be prepared by reaction of praseodymium and antimony at high temperature:
Pr + 2 Sb → PrSb2
The Pr–Sb phase diagram contains PrSb2 together with several more praseodymium-rich antimonides, including PrSb, Pr4Sb3 and Pr5Sb3.
Properties Crystal structure PrSb2 crystallizes in the orthorhombic crystal system with the SmSb2-type structure, space group Cmce (No. 64), historically written Cmca. Representative lattice parameters are a = 6.224 Å, b = 6.127 Å and c = 18.144 Å, with eight formula units per unit cell. The calculated density is approximately 7.38 g/cm3. The structure is strongly layered and contains two crystallographically distinct antimony sites. It is closely related to the structures of other light rare-earth diantimonides and to the ZrSi2 structural family.
Phase stability and thermochemistry PrSb2 forms peritectically at approximately 1100 °C rather than melting congruently. The standard enthalpy of formation has been measured calorimetrically. Borzone et al. reported approximately −97 kJ per mole of atoms, corresponding to about −291 kJ mol−1 of PrSb2.
Electronic properties PrSb2 is a metallic, strongly anisotropic conductor. Its in-plane electrical resistivity is substantially lower than that along the crystallographic c axis, reflecting the nearly two-dimensional electronic structure. The resistivity shows a pronounced anomaly near 100 K. Later Raman-scattering, X-ray-diffraction and transport measurements established that this anomaly corresponds to formation of a charge-density wave. Below the transition, a collective amplitude mode appears in the Raman spectrum. X-ray diffraction shows changes in the thermal evolution of the lattice parameters near 100 K but no change in crystallographic symmetry, indicating strong coupling between the electronic instability and the lattice.
Magnetic properties PrSb2 orders antiferromagnetically at approximately 5.1 K. The magnetic response is strongly anisotropic as a result of crystal-field splitting of the Pr3+ levels. Applied magnetic fields in the ordered phase produce metamagnetic transitions. Two transitions have been observed near 0.4 T and 1.4 T under ambient pressure. Hydrostatic pressure increases the Néel temperature, with reported pressure coefficients of approximately 1.3–1.6 K GPa−1. Hall-effect measurements have more recently found an additional contribution to the Hall resistivity within the antiferromagnetic phase, interpreted as a topological Hall effect. The effect weakens under pressure and nearly disappears when the charge-density-wave state is suppressed near 1 GPa.
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