Ferromagnetism and spin-glass-like behavior in (Nd0.65Y0.35)0.7Sr0.3MnO3

Abstract

We have studied the ferromagnetism and spin-glass-like behavior in polycrystalline perovskite (Nd0.65Y0.35)0.7Sr0.3MnO3 based on investigations of the magnetization, magnetic AC susceptibility, and electron spin resonance (ESR). Magnetization measurements versus temperature reveal a spin-glass phase-transition temperature Tg at about 53 K. For the in-phase susceptibility x′(T), a frequency-dependent peak called the spin-freezing temperature Tf is observed. A lowering of the frequency to zero leads to Tf → Tg. The dynamics of this process was analyzed by means of the slowing-down scaling law τ/τo = (Tf /Tg-1)−zv, where the characteristic time τo and critical exponent zv obtained by fitting the experimental Tf data were about (i.e., 1.6 × 10−15 s) and 10.12, respectively, quite different from those expected for canonical spin-glass systems with τo = 10−13 s and zv = 10. The spin-glass phenomenon is related to the magnetic frustration phenomenon caused by strong competition between ferromagnetic and anti-ferromagnetic interactions, together with the strong magnetic disorder. The dynamics of the magnetic interactions in (Nd0.65Y0.35)0.7Sr0.3MnO3 was studied further by means of ESR.