Probing the magnetic state by linear and non-linear ac magnetic susceptibility measurements in under-doped manganite Nd0.8Sr0.2MnO3

Abstract

a b s t r a c tWe have thoroughly investigated the entire magnetic states of under-doped ferromagnetic-insulating manganite Nd 0.8 Sr 0.2 MnO 3 through temperature-dependent linear and non-linear complex ac magnetic susceptibility measurements. This ferromagnetic-insulating manganite is found to have frequencyindependent ferromagnetic to paramagnetic transition temperature at around 140 K. At around 90 K (E T e ) the sample shows a second frequency-dependent re-entrant magnetic transition as explored through complex ac susceptibility measurements. Non-linear ac susceptibility measurements (higher harmonics of ac susceptibility) have also been performed (with and without the superposition of a dc magnetic field) to further investigate the origin of this frequency dependence (dynamic behavior at this re-entrant magnetic transition). Divergence of 3rd harmonic of ac susceptibility in the limit of zero exciting field indicates a spin-glass-like freezing phenomena. However, large value of spin-relaxation time (t 0 =10 À 8 s) and small value of coercivity ($ 22 Oe) obtained at low temperature (below T e ) from critical slowing down model and dc magnetic measurements, respectively, are in contrast with what generally observed in a canonical spin glass (t 0 =10 À 12 -10 À 14 s and very large value of coercivity below freezing temperature). We have attributed our observation to the formation of finite size ferromagnetic clusters which are formed as consequence of intrinsic phase separation and undergo cluster glass-like freezing below certain temperature in this under-doped manganite. The results are supported by the electronic-and magneto-transport data.

Optimization of Pr0.9Ca0.1MnO3thin films and observation of coexisting spin-glass and ferromagnetic phases at low temperature

“…The intensity of the first peak in χ (T) also decreases and shifts towards lower temperature with increasing frequency. This frequency shift in T p is rather unusual for the conventional spin-glasses, where generally the peak shifts towards higher temperature with increasing frequency [39]. The shape of the temperature dependent χ curve is completely different to that of χ .…”

Linear and nonlinear ac susceptibilities in polycrystalline low-bandwidth Pr1−xCaxMnO3(x= 0.0 − 0.3) manganite

“…The magnetization m of the FM system near the critical temperature when excited by a small ac magnetic field h can be expressed as [14,25,27]…”

“…The theoretical calculations based on mean field theory [20][21][22][23] predict different behavior of nonlinear ac susceptibility χ n (n = 2, 3, ...) in the magnetic phase transition region in SG, ferromagnets and antiferromagnets. Hence, nonlinear ac susceptibility χ n has become an efficient experimental method for distinguishing the different magnetic orderings [14], [24][25][26][27]. Earlier, the systematic doping-concentration-dependent evolution of the frustrated magnetic phase was reported for low bandwidth manganite Nd 1−x Ca x MnO 3 [28,29] and Nd 1−x Sr x MnO 3 [27,30], though for PCMO most ac-susceptibility studies concentrated on the higher hole doping regime in the vicinity of the CO phase [30][31][32][33].…”

“…Hence, nonlinear ac susceptibility χ n has become an efficient experimental method for distinguishing the different magnetic orderings [14], [24][25][26][27]. Earlier, the systematic doping-concentration-dependent evolution of the frustrated magnetic phase was reported for low bandwidth manganite Nd 1−x Ca x MnO 3 [28,29] and Nd 1−x Sr x MnO 3 [27,30], though for PCMO most ac-susceptibility studies concentrated on the higher hole doping regime in the vicinity of the CO phase [30][31][32][33]. Also the effect of the dc magnetic field on the domain wall motion and the non-linear ac susceptibility for the low-hole doping range of PCMO has not been studied.…”

Probing the SmRhSn magnetic state by AC/DC magnetic measurements and 119Sn Mössbauer spectroscopy

“…Increasing of the magnetic field remarkably reduces the transition temperature. These peak shifts can be connected with some intrinsic domains or cluster phenomena [ 23,24]. The temperature determined for a maximum obtained for the lowest H ac ¼ 1 Oe (T C ¼ 14.9(2) K) can be assumed as a temperature of transition from a paramagnetic to a magnetically ordered state.…”