Ferromagnetic cluster behaviors and magnetoresistance in Ni-doped LaSrMnO3 systems

Abstract

We have studied the magnetic and magnetotransport properties of the perovskites La8Sr0.2Mn8Ni0.2O3 and La0.7Sr0.3Mn0.8Ni0.2O3. Ferromagnetic cluster behaviors have been observed. The most interesting feature is that the cluster-glass state exhibits both macroscopic insulator-like transport behavior and largely enhanced magnetoresistance (MR) at low temperature. Such a low-temperature MR is weakly temperature dependent. In particular, a low-temperature magnetoresistance ratio (Δρ/ρ0) as high as 60% has been found in La0.7Sr0.3Mn0.8Ni0.2O3. We attribute the low-temperature magnetotransport to the spin-dependent scattering inside the grains.

Electrical conductivity and low field magnetoresistance in polycrystalline La1−xKxMnO3 pellets prepared by pyrophoric method

“…Magnetoresistance due to spin-polarized tunneling contributes to a sharp drop in resistance at low fields and is dominant at low temperatures (T/T C ), on the other hand, the intrinsic part is pronounced near T C . This low field low temperature MR is also expected to be observed in ferromagnetic cluster perovskite due to the existence of cluster surface or, insulating regions between ferromagnetic metallic clusters [47]. Hwang et al [6] originally suggested that the observed low field decrease in resistance is the result of progressive alignment of the magnetic domains associated with the grains by the movement of the domain walls across the grain boundaries.…”

Magnetic properties and low-field magnetoresistance of La0.7Sr0.3Mn0.9M0.1O3 compounds (M=Al, Cr, Mn, Fe, Co, Ni, Cu, and Ga)

“…Tel. : +86 10 62521523; fax: +86 10 62517887. substitution by various other ions such as Al [14,15], or transition metals Cr [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], Fe [18,20,[31][32][33][34][35][36][37][38][39][40][41], Co [20,25,[42][43][44][45][46][47][48], Ni [20,37,[49][50][51][52][53], Cu [20,[54][55][56][57][5...…”

Structural and magnetic properties of La0.7Sr0.3Mn1−xNixO3 (x ≤ 0.4)

“…The differences between M ZFC and M FC curves have routinely been ascribed to spin glass, spin clusters or re-entrant spin glass. 23,24,29 However, we believe that these differences are actually due to charge ordering and the complex competition between the Ni 3þ -O-Mn 3þ ferromagnetic couplings and the Ni 3þ -O-Mn 4þ and Ni 3þ -O-Ni 3þ antiferromagnetic couplings. For x ¼ 0.08 and 0.16, the applied magnetic field coerces a magnified magnetic response while at x ¼ 0.21, it suppresses the weakly charge ordered state as was observed by Tomioka et al 31 in the Pr 0.5 Sr 0.5 MnO 3 system.…”

“…Further, they found the metal-to-insulator transition to occur between x ¼ 0.15 and x ¼ 0.20 with x ¼ 0.20 to be completely insulating, and with increased Ni content, a reduction of T C , cell parameters, volume and an increase in the temperature differences between T C and the metal-to-insulator transition. In their study of La 0.70 Sr 0.30 Mn 1Àx Ni x O 3 , Feng et al 24 found the metal-to-insulator transition occurring at x $ 0.20, with T C and magnetization decreasing with increasing Ni content. They also found saturation magnetization values smaller than the calculated values assuming the Ni ion to be ferromagnetically coupled to the Mn ions.…”