Suppression of itinerant ferromagnetism and a spin-glass-like state in Zn substitutedLa0.67Ca0.33MnO3

Abstract

We examine the magneto-transport, static and dynamic magneticresponses of the single phase glassy insulating compoundLa0.67Ca0.33Mn1 − xZnxO3 (x = 0.10). Thiscompound undergoes a field induced metal–insulator transition and exhibits colossal magnetoresistancefor H ≥ 2 T. Many experimental features, such as a frequency dependent cusp inthe in-phase component of linear ac susceptibility at a temperatureT′f, a broadmaximum (at Ta) in the ZFC cooled thermo-magnetization close toT′f, large thermo-magneticirreversibility below Ta, non-saturation of magnetization at 5 K even under 12 T with a characteristic S shape in the virgincurve, monotonic increase of the coercivity at low fields under ZFC condition as one approaches theT′f, logarithmic relaxation of thermo-magnetization and ageing effects belowTa and a characteristic maximum in the magnetic viscosity below the spin-glass transition temperature(Tg) indicate a spin-glass-like state at low temperatures. This is further substantiated by theabsence of second order non-linear ac susceptibility, a characteristic negative maximum atTg in third order non-linearac susceptibility (χ′3), thecritical divergence of χ′3 as a function of temperature and ac probe field and an unusually large linear term in thelow temperature specific heat.