High-pressure Synthesis and Physical Characterization of Y-based 1222-type Niobio–Cuprate NbSr 2 (Y 1.5 Ce 0.5 )Cu 2 O 10

We have successfully synthesized a new 1222-type Y-based niobio-cuprate for the first time with the chemical composition, NbSr 2 (Y 1.5 Ce 0.5 )Cu 2 O 10 by a high-pressure and high-temperature (HPHT) technique under different synthesis conditions. Good quality (nearly single-phase) Nb1222Y polycrystalline sample was synthesized at 1,450 ○ C and 6 GPa for 2 h. It crystallizes in a tetragonal symmetry of space group I4/ mmm with lattice parameters a = b =3.863(2) Å and c =28.687(5) Å, which is isostructural with the corresponding Ru1222Y (RuSr 2 (Y 1.5 Ce 0.5 )Cu 2 O 10 ) phase. The dc -magnetic susceptibility measurements show a mixed magnetic state at ∼29 K, which is apparently associated with magneto-superconductivity . The magnetic moment ( M ) versus field ( H ) curve of Nb1222Y sample measured at 1.8 K looks like a hybrid and it normally ensembles for both superconducting and a ferromagnetic curve. As the field increases, a low field diamagnetic signal emerges. However, temperature dependence of electrical resistivity of Nb1222Y did not show superconductivity, but semiconducting nature with a relatively large magnetoresistance (∼6% at almost entire region). No specific heat anomaly was observed at the vicinity of the transition temperature.