High-pressure synthesis and magnetic properties of the niobio-cuprate Nb0.9Sr2HoCu2.1O7.9

Ho-based 1212 niobio-cuprate (Nb-1212Ho) was synthesized for the first time. An off-stoichiometric starting composition Nb0.9Sr2HoCu2.1O7.9 led a phase-pure polycrystalline sample under the synthesis condition at 1450 °C for 2 h at 6 GPa, approximating the true bulk composition. X-ray diffraction pattern clearly indicated an Nb-1212 type structure for the compound with lattice parameters a = b = 3.8505(1) Å and c = 11.574(3) Å, suggesting that the space group P4/mmm is likely for the structure. Unlike Nb-1212Y, the Nb-1212Ho compound showed neither superconductivity nor a magnetic order down to 1.8 K. A relatively large magneto-resistance approximately −7% was found at 30 K.