Low temperature magnetic and anomalous high temperature dielectric response of Dy–Ni co-doped hexagonal YMnO3 ceramics

Abstract YMnO 3 pristine and Dy–Ni co-doped Y 1− x Dy x Mn 1− x Ni x O 3 compositions with x =0.01, 0.03 and 0.05 were synthesised by high temperature solid state route. In all synthesized samples with doping a minor phase of DyMnO 3 is formed but no indication of phase transition from hexagonal to orthorhombic is observed. For 3 and 5% Dy–Ni co-doped YMnO 3 , a thin coercivity is observed at 10 K due to insertion of weak ferromagnetism in these compositions. For undoped YMnO 3 , crimps are observed in both FC and ZFC curves at exactly 75 K (Neel temperature), however crimps are shifted towards significantly lesser temperature after adding the dopants. For pristine and 1% Dy–Ni co-doped samples explicit bifurcation in FC–ZFC curves is observed, which is not pronounced for 3 and 5% Dy–Ni co-doped samples. Moreover, in these compositions cusps are observed only in ZFC curves at 25 and 19 K, respectively which can be considered as hallmark of weak spin glass behaviour in these compositions. Anomalous dielectric peaks are observed at 450 and 550 K for undoped YMnO 3 while a distinct peak is observed at 450 K for 1% Dy–Ni co-doped sample along with the suppression of other peaks. It is proposed that relaxor behaviour of these peaks can be explained on the basis of the Maxwell–Wagner effect.