Yu. A. Velikodny

Magnetic properties of Cu2V2O7

Abstract Magnetic measurements were performed on Cu2V2O7. Above ∼70 K paramagnetic susceptibility obeys the Curie–Weiss law. Value of effective magnetic moment μeff=1.9μB corresponds to that of Cu2+. The Weiss temperature Θ=−66 K is negative and indicates an antiferromagnetic exchange interaction between Cu2+ ions. At T c =35 K a spontaneous magnetization arises due to the transition from paramagnetic state into either ferrimagnetic or canted antiferromagnetic state.

Superconductivity of Fullerides AnHgxC60 (A = K,Rb,Cs; n = 2,3) Synthesized from Amalgams

The fullerides AnHgxC60 (A = K,Rb,Cs; n = 2,3; x<1) have been synthesized by a new method using liquid alloys of metals with mercury (amalgams). It was found that the fulleride K2HgxC60 is superconductor with transition temperature Tc = 22 K that exceeds Tc for K3C60 (19 K). The fulleride K3HgxC60 is not superconductor and has monoclinic crystal lattice. The fullerides RbnHgxC60 (n = 2,3) are superconductors with Tc = 24–25 K that is less than Tc = 28 K for Rb3C60. The fullerides with composition CsnHgxC60 (n = 2,3) are not superconductors and crystallize in orthorhombic lattices. The density of electronic states at Fermi energy was estimated from EPR data.

Lead lanthanum and strontium lanthanum germanovanadates with apatite and oxyapatite structures

New compounds Pb4La(GeO4)2(VO4)(I) and Sr5La5(GeO4)5(VO4)O(II) were prepared and identified. Compound I has the structure of apatite, a = 10.108(1) Å, c = 7.369(1) Å, V = 652.1(2) Å3. Compound II has the structure of oxyapatite, a = 9.9028(5) Å, c = 7.3162(4) Å, V = 621.34(6) Å3.

Mutual cation substitutions in palmierite orthovanadates: M3(VO4)2–M2Me2/3(VO4)2 systems where M = Sr, Ba, or Pb and Me = La or Bi

We performed the synthesis and studied the extents and compositions of solid solutions (ss) formed by heterovalent substitutions in M3(VO4)2–M2Me2/3(VO4)2 systems where M = Sr, Ba, or Pb and Me = La or Bi. A continuous solid solution (css) series was shown to be formed only when the initial compounds crystallize in palmierite structure. Bi3+ and La3+ were shown to occupy different positions (3а and 6с, respectively) in the crystal lattice of Sr3(VO4)2-base ss.

Short-range and long-range magnetic ordering in α-CuV2O6

Abstract Magnetic properties of α-CuV2O6 with linear chains of edge-sharing CuO6 octahedra were studied by magnetic susceptibility and electron spin resonance measurements. The broad maximum of magnetic susceptibility at T M =44 K , corresponding to the intrachain exchange interaction J 1 =34 K , indicates one-dimensional short-range magnetic ordering within the chains. Three-dimensional long-range antiferromagnetic ordering takes place at T N =24 K suggesting a rather big value for the interchain exchange interaction J 2 ∼13 K . The 76 GHz energy gap, found in the antiferromagnetic resonance spectrum, agrees with the spin-flop magnetic field value of about 2.7 T.