MAGNETIC ORDER INDUCED BY HYDROGEN IN SUPERCONDUCTING RBA(2)CU(4)O(8) (R=Y,GD) STUDIED BY MOSSBAUER AND NQR TECHNIQUES

Magnetic susceptibility, Mössbauer spectroscopy, nuclear quadrupole resonance of Cu (NQR), nuclear magnetic resonance of Cu in the hyperfine field of the antiferromagnetic state (AFNMR), and x-ray diffraction measurements were performed to study the superconducting and magnetic properties of hydrogen charged bulk YBa2Cu4O8Hy. For y<1 the c lattice parameter decreases with y. In contrast to Fe-doped YBa2Cu3O7Hy, where Tc decreases continuously with increasing y, we find here that for 1% Fe doped, Tc=59 K is unaffected by hydrogen charging, but the shielding fraction is reduced sharply from 38% for y=0 to 17% and 3% for y=1 and 1.85, respectively. The Mössbauer spectra for y=0 at T>90 K contain one doublet. The spectra for hydrogen charged samples, in addition to this doublet, contain a magnetic pattern composed of two sextets, between 4.1 K and TN=360 K. The relative amount of the magnetic pattern depends on hydrogen concentration. The Mössbauer spectrum obtained for y=1 is a superposition of spectra obtained for y=0 and those for y=2, showing a phase separation into magnetic and superconducting regions in YBa2Cu4O8Hy. NQR-AFNMR studies of YBa2Cu4O8Hy and GdBa2Cu4O8Hy samples indicate that magnetic order is induced only in the Cu(2) planes. © 1994 The American Physical Society.